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| author | Roger Frank <rfrank@pglaf.org> | 2025-10-14 19:56:49 -0700 |
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| committer | Roger Frank <rfrank@pglaf.org> | 2025-10-14 19:56:49 -0700 |
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diff --git a/31987-h/31987-h.htm b/31987-h/31987-h.htm new file mode 100644 index 0000000..1e1dd61 --- /dev/null +++ b/31987-h/31987-h.htm @@ -0,0 +1,12078 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" +"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"> +<head> +<meta name="generator" content="HTML Tidy, see www.w3.org" /> +<meta http-equiv="Content-Type" content= +"text/html;charset=utf-8" /> +<title>Territory in +Bird Life +by H. Eliot Howard.</title> +<style type="text/css"> + + p { margin-top: .75em; + text-align: justify; + margin-bottom: .75em; + } + + p.tb { margin-top: .75em; + text-align: justify; + margin-bottom: 1.50em; + } + + p.tb2 { margin-top: .75em; + text-align: justify; + margin-bottom: 1.50em; font-size: .85em; + } + + + p.indent { margin-top: 0em; margin-bottom: .75em; + text-align: justify; margin-left: 2em; text-indent: -2em;} + + p.indent2 { margin-top: .75em; margin-bottom: 0em; + text-align: justify; margin-left: 2em; text-indent: -2em;} + + h1 {letter-spacing: 5px; text-align: center; margin-bottom:0em; font-weight: normal; /* all headings centered */ + clear: both; } + + p.underline { margin-top: 0em; margin-bottom: .75em; + text-align: center; text-decoration: underline;} + p.center { margin-top: 0em; margin-bottom: .75em; + text-align: center;} + + h2,h3,h4, h5, h6 { + text-align: center; margin-bottom:0em; font-weight: normal; /* all headings centered */ + clear: both; + } + + hr { width: 33%; + margin-top: 1.5em; + margin-bottom: 1.5em; + margin-left: auto; + margin-right: auto; + clear: both; + } + + + small {font-size: .7em;} + + td.left { padding-top: 0em; padding-bottom: 0em; font-size: .9em; text-align: left; width: 90%;} + td.right { padding-top: .0em; padding-bottom: 0em; font-size: .9em; padding-bottom: .75em; text-align: right; width: 10%; vertical-align: bottom;} + td.right2 { padding-top: .0em; font-size: .9em; text-align: right; width: 10%; vertical-align: bottom;} + td.left50 { padding-top: 0em; padding-bottom: 0em; font-size: 1em; text-align: left; width: 50%; vertical-align: top;} + td.center50 { padding-top: 0em; padding-bottom: 0em; font-size: .9em; text-align: center; width: 50%; vertical-align: top;} + body {margin-left: 10%; margin-right: 10%; } + + .pagenum { /* uncomment the next line for invisible page numbers */ + /* visibility: hidden; */ + position: absolute; + right: 4%; font-style: normal; + font-size: .8em; + text-align: right; + } /* page numbers */ + + .box {border: 1px; border: 1px solid; border-color: gray; + font-size: .9em; margin-left: 5%; margin-right: 5%; + padding-left: 1em; padding-right: 1em; + + padding-top: 1em; padding-bottom: 1em;} + table {margin-left: auto; margin-right: auto;} + + ul {list-style-type: none;} + ul.IX { /* styling the IndeX */ + list-style-type: none; margin-top: .2em; + text-indent: 0em; font-size: .9em; + } + ul.IX li { /* list items in an index list: compressed */ + margin-top: .3em; text-indent: -1em; font-size: 1em; } + ul.IX li4 { /* list items in an index list: compressed */ + margin-top: .1em; } + + .figcenter {margin: auto; text-align: center; margin-top: 2em;} + .figcenter2 {margin: auto; border: 2px solid black; text-align: center; margin-top: 2em;} + + + .caption {font-size: .9em; text-align: center; margin-top: 1em; + margin-bottom: 1em; margin-left: 5%; margin-right: 5%; + } + + + .box {border: 1px; border: 1px solid; border-color: gray; + font-size: .9em; margin-left: 5%; margin-right: 5%; + padding-left: 2em; padding-right: 2em;} + + + .smcap {font-variant: small-caps;} + .smcaplc {font-variant: small-caps; text-transform: lowercase;} + .u {text-decoration: underline;} + + img {border: 0; } + img.center {height: 3.5em; vertical-align: middle;} + + small {font-size: .7em;} + + .footnote {margin-left: 12%; margin-right: 10%; font-size: 0.9em;} + .footnote .label {position: absolute; right: 83%; text-align: right; font-size: .8em;} + .fnanchor {vertical-align: super; font-size: .6em; text-decoration: none;} + +</style> +</head> +<body> + + +<pre> + +The Project Gutenberg EBook of Territory in Bird Life, by H. Eliot Howard + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Territory in Bird Life + +Author: H. Eliot Howard + +Illustrator: G. E. Lodge + H. Grönvold + +Release Date: April 14, 2010 [EBook #31987] + +Language: English + +Character set encoding: UTF-8 + +*** START OF THIS PROJECT GUTENBERG EBOOK TERRITORY IN BIRD LIFE *** + + + + +Produced by Chris Curnow, Turgut Dincer, Joseph Cooper and +the Online Distributed Proofreading Team at +https://www.pgdp.net + + + + + + +</pre> + +<p> </p> +<div class="box"> +<p>TRANSCRIBER'S NOTE:<br /> +There are a large number of compound words in +this book including bird names which occur joined, +spaced and hyphenated. No attempt has been made to +correct these discrepancies as these are mostly +alternative spellingd of thw same word. In the case of bird names it +is difficult to decide as ornithologists are +still debating on this subject.</p> +</div> + + +<h3><br />TERRITORY IN BIRD LIFE</h3> + +<div class="figcenter" style="width: 500px;"><a name="f004" id="f004"></a><img src="images/fig004.jpg" width="500" height="808" +alt="A pair of Lesser Spotted Woodpeckers +attacking a Great Spotted Woodpecker." title="A pair of Lesser Spotted Woodpeckers +attacking a Great Spotted Woodpecker" /></div> + +<h1> +TERRITORY IN<br /> +BIRD LIFE</h1> + +<h3>BY H. ELIOT HOWARD</h3> + + +<h4>WITH ILLUSTRATIONS BY<br /> +G. E. LODGE AND H. GRÖNVOLD</h4> + +<h5>NEW YORK<br /> +<big>E. P. DUTTON AND COMPANY</big><br /> +1920</h5> + +<p><span class='pagenum'><a name="Page_v" id="Page_v">v</a></span></p> +<hr /> +<h3>PREFACE</h3> + + +<p>When studying the Warblers some twenty +years ago, I became aware of the fact that +each male isolates itself at the commencement +of the breeding season and exercises dominion +over a restricted area of ground. Further investigation, +pursued with a view to ascertaining +the relation of this particular mode of behaviour +to the system of reproduction, led to my studying +various species, not only those of close affinity, +but those widely remote in the tree of avian +life. The present work is the outcome of +those investigations. In it I have endeavoured +to interpret the prospective value of the behaviour, +and to trace out the relationships in +the organic and inorganic world which have +determined its survival. Much is mere speculation; +much with fuller knowledge may be +found to be wrong. But I venture to hope +that a nucleus will remain upon which a more +complete territorial system may one day be +established.<span class='pagenum'><a name="Page_vi" id="Page_vi">vi</a></span></p> + +<p>I have to thank Mr. G. E. Lodge and Mr. +H. Grönvold for the trouble they have taken +in executing my wishes; I also want to record +my indebtedness to the late E. W. Hopewell; +and to Professor Lloyd Morgan, F.R.S., I am +beholden more than I can tell.</p> +<hr /> +<p><span class='pagenum'><a name="Page_vii" id="Page_vii">vii-viii</a></span></p> +<h3>CONTENTS</h3> + +<table width="100%" summary="toc" border="0"> +<tr> +<td class="left"> </td> +<td class="right"><small>PAGE</small></td> +</tr><tr> +<td class="center50" colspan="2">CHAPTER I</td> +</tr><tr> +<td class="left"><p class="indent"><span class="smcap">Introduction</span></p></td> +<td class="right"><a href="#Page_1">1</a></td> +</tr><tr> +<td class="center50" colspan="2">CHAPTER II</td> +</tr><tr> +<td class="left"><p class="indent"><span class="smcap">The Disposition to Secure a Territory</span></p></td> +<td class="right"><a href="#Page_20">20</a></td> +</tr><tr> +<td class="center50" colspan="2">CHAPTER III</td> +</tr><tr> +<td class="left"><p class="indent"><span class="smcap">The Disposition to Defend the Territory</span></p></td> +<td class="right"><a href="#Page_73">73</a></td> +</tr><tr> +<td class="center50" colspan="2">CHAPTER IV</td> +</tr><tr> +<td class="left"><p class="indent"><span class="smcap">The Relation of Song to the Territory</span></p></td> +<td class="right"><a href="#Page_119">119</a></td> +</tr><tr> +<td class="center50" colspan="2">CHAPTER V</td> +</tr><tr> +<td class="left"><p class="indent"><span class="smcap">The Relation of the Territory to the System of +Reproduction</span></p></td> +<td class="right"><a href="#Page_169">169</a></td> +</tr><tr> +<td class="center50" colspan="2">CHAPTER VI</td> +</tr><tr> +<td class="left"><p class="indent"><span class="smcap">The Warfare between Different Species and its +Relation to the Territory</span></p></td> +<td class="right"><a href="#Page_215">216</a></td> +</tr><tr> +<td class="center50" colspan="2">CHAPTER VII</td> +</tr><tr> +<td class="left"><p class="indent"><span class="smcap">The Relation of the Territory to Migration</span></p></td> +<td class="right"><a href="#Page_259">259</a></td> +</tr><tr> +<td class="left"><p class="indent"><span class="smcap">Index</span></p></td> +<td class="right"><a href="#Page_302">302</a></td> +</tr></table> +<hr /> +<p><span class='pagenum'><a name="Page_ix" id="Page_ix">ix</a></span></p> + +<h3>LIST OF ILLUSTRATIONS</h3> + +<table width="100%" summary="illustrations" border="0"> +<tr> +<td class="left"> </td> +<td class="right2"><i>Faces page</i></td> +</tr><tr> +<td class="left"><p class="indent2">A pair of Lesser Spotted Woodpeckers attacking a Great +Spotted Woodpecker</p></td> +<td class="right2"><a href="#f004"><i>Frontispiece</i></a></td> +</tr><tr> +<td class="left"><p class="indent2">Territorial flight of the Black-tailed Godwit</p></td> +<td class="right2"><a href="#f073">54</a></td> +</tr><tr> +<td class="left"><p class="indent2">Competition for territory is seldom more severe than +individual Razorbills to secure positions on the +among cliff-breeding seabirds, and the efforts of +crowded ledges lead to desperate struggles</p></td> +<td class="right2"><a href="#f089">64</a></td> +</tr><tr> +<td class="left"><p class="indent2">Male Blackbirds fighting for the possession of territory. +The bare skin on the crown of the defeated bird shows +the nature of the injuries from which it succumbed.</p></td> +<td class="right2"><a href="#f101">74</a></td> +</tr><tr> +<td class="left"><p class="indent2">Male Cuckoos fighting before the arrival of a female</p></td> +<td class="right2"><a href="#f111">82</a></td> +</tr><tr> +<td class="left"><p class="indent2">Two pairs of Pied Wagtails fighting in defence of their +territories</p></td> +<td class="right2"><a href="#f117">86</a></td> +</tr><tr> +<td class="left"><p class="indent2">Long-tailed Tit: males fighting for the possession of +territory. The feathers have been torn from the crown +of the defeated and dying rival</p></td> +<td class="right2"><a href="#f129">96</a></td> +</tr><tr> +<td class="left"><p class="indent2">A battle between two pairs of Jays</p></td> +<td class="right2"><a href="#f141">106</a></td> +</tr><tr> +<td class="left"><p class="indent2">The Female Chaffinch shares in the defence of the territory +and attacks other females</p></td> +<td class="right2"><a href="#f147">110</a></td> +</tr><tr> +<td class="left"><p class="indent2">Peregrine Falcon attacking a Raven</p></td> +<td class="right2"><a href="#f255">216</a></td> +</tr><tr> +<td class="left"><p class="indent2">A battle between a pair of Green Woodpeckers and a +Great Spotted Woodpecker for the possession of a hole +in an oak-tree</p></td> +<td class="right2"><a href="#f281">238</a></td> +</tr> +</table> +<hr /> +<table width="100%" summary="illustrations" border="0"> +<tr> +<td class="left"><p class="indent2">Plans of the Water-meadow showing the Territories +occupied by Lapwings in 1915 and 1916</p></td> +<td class="right2"><a href="#f080"><i>Between</i> 58 and 59</a></td> +</tr> +</table> + +<hr /> + +<p><span class='pagenum'><a name="Page_xi" id="Page_xi">x-xi</a></span></p> + +<h3>SCIENTIFIC NAMES OF BIRDS<br /> +MENTIONED IN THE TEXT<br /><br /></h3> + +<table width="100%" summary="scientific names" border="0"> +<tr> +<td class="left50">Raven</td> +<td class="left50"><i>Corvus corax.</i></td> +</tr><tr> +<td class="left50">Carrion-Crow</td> +<td class="left50"><i>Corvus corone.</i></td> +</tr><tr> +<td class="left50">Hooded Crow</td> +<td class="left50"><i>Corvus cornix.</i></td> +</tr><tr> +<td class="left50">Rook</td> +<td class="left50"><i>Corvus frugilegus.</i></td> +</tr><tr> +<td class="left50">Magpie</td> +<td class="left50"><i>Pica pica.</i></td> +</tr><tr> +<td class="left50">Jay</td> +<td class="left50"><i>Garrulus glandarius rufitergum.</i></td> +</tr><tr> +<td class="left50">Chough</td> +<td class="left50"><i>Pyrrhocorax pyrrhocorax.</i></td> +</tr><tr> +<td class="left50">Starling</td> +<td class="left50"><i>Sturnus vulgaris.</i></td> +</tr><tr> +<td class="left50">Greenfinch</td> +<td class="left50"><i>Chloris chloris.</i></td> +</tr><tr> +<td class="left50">Hawfinch</td> +<td class="left50"><i>Coccothraustes coccothraustes.</i></td> +</tr><tr> +<td class="left50">House-Sparrow</td> +<td class="left50"><i>Passer domesticus.</i></td> +</tr><tr> +<td class="left50">Chaffinch</td> +<td class="left50"><i>Fringilla cœlebs.</i></td> +</tr><tr> +<td class="left50">Brambling</td> +<td class="left50"><i>Fringilla montifringilla.</i></td> +</tr><tr> +<td class="left50"> +Linnet</td><td class="left50"><i>Acanthis cannabina.</i></td> +</tr><tr> +<td class="left50"> +Corn-Bunting</td><td class="left50"><i>Emberiza calandra.</i></td> +</tr><tr> +<td class="left50"> +Yellow Bunting</td><td class="left50"><i>Emberiza citrinella.</i></td> +</tr><tr> +<td class="left50"> +Cirl Bunting</td><td class="left50"><i>Emberiza cirlus.</i></td> +</tr><tr> +<td class="left50"> +Reed-Bunting</td><td class="left50"><i>Emberiza schœniclus.</i></td> +</tr><tr> +<td class="left50"> +Sky-Lark</td><td class="left50"><i>Alauda arvensis.</i></td> +</tr><tr> +<td class="left50"> +Pied Wagtail</td><td class="left50"><i>Motacilla lugubris.</i></td> +</tr><tr> +<td class="left50"> +Tree-Pipit</td><td class="left50"><i>Anthus trivialis.</i></td> +</tr><tr> +<td class="left50"> +Meadow-Pipit</td><td class="left50"><i>Anthus pratensis.</i></td> +</tr><tr> +<td class="left50"> +Great Titmouse</td><td class="left50"><i>Parus major newtoni.</i></td> +</tr><tr> +<td class="left50"> +Blue Titmouse</td><td class="left50"><i>Parus cœruleus obscurus.</i></td> +</tr><tr> +<td class="left50"> +Long-tailed Titmouse</td><td class="left50"><i>Ægithalus caudatus roseus.</i></td> +</tr><tr> +<td class="left50"> +Red-backed Shrike</td><td class="left50"><i>Lanius collurio.</i></td> +</tr><tr> +<td class="left50"> +Whitethroat</td><td class="left50"><i>Sylvia communis.</i></td> +</tr><tr> +<td class="left50"> +<span class='pagenum'><a name="Page_xii" id="Page_xii">xii</a></span> +Lesser Whitethroat</td> +<td class="left50"><i>Sylvia curruca.</i></td> +</tr><tr> +<td class="left50"> +Blackcap</td> +<td class="left50"><i>Sylvia atricapilla.</i></td> +</tr><tr> +<td class="left50"> +Grasshopper-Warbler</td> +<td class="left50"><i>Locustella nœvia.</i></td> +</tr><tr> +<td class="left50"> +Savi's Warbler</td> +<td class="left50"><i>Locustella luscinioides.</i></td> +</tr><tr> +<td class="left50"> +Reed-Warbler</td> +<td class="left50"><i>Acrocephalus scirpaceus.</i></td> +</tr><tr> +<td class="left50"> +Marsh-Warbler</td> +<td class="left50"><i>Acrocephalus palustris.</i></td> +</tr><tr> +<td class="left50"> +Sedge-Warbler</td> +<td class="left50"><i>Acrocephalus schœnobænus.</i></td> +</tr><tr> +<td class="left50"> +Willow-Warbler</td> +<td class="left50"><i>Phylloscopus trochilus.</i></td> +</tr><tr> +<td class="left50"> +Wood-Warbler</td> +<td class="left50"><i>Phylloscopus sibilatrix.</i></td> +</tr><tr> +<td class="left50"> +Chiffchaff</td><td class="left50"><i>Phylloscopus collybita.</i></td> +</tr><tr> +<td class="left50"> +Song-Thrush</td> +<td class="left50"><i>Turdus musicus clarkii.</i></td> +</tr><tr> +<td class="left50"> +Redwing</td> +<td class="left50"><i>Turdus iliacus.</i></td> +</tr><tr> +<td class="left50"> +Blackbird</td> +<td class="left50"><i>Turdus merula.</i></td> +</tr><tr> +<td class="left50"> +Redstart</td> +<td class="left50"><i>Phœnicurus phœnicurus.</i></td> +</tr><tr> +<td class="left50"> +Redbreast</td><td class="left50"><i>Erithacus rubecula melophilus.</i></td> +</tr><tr> +<td class="left50"> +Nightingale</td> +<td class="left50"><i>Luscinia megarhyncha.</i></td> +</tr><tr> +<td class="left50"> +Stonechat</td> +<td class="left50"><i>Saxicola rubicola.</i></td> +</tr><tr> +<td class="left50"> +Whinchat</td><td class="left50"><i>Saxicola rubetra.</i></td> +</tr><tr> +<td class="left50"> +Wheatear</td><td class="left50"><i>Œnanthe œnanthe.</i></td> +</tr><tr> +<td class="left50"> +Hedge-Sparrow</td> +<td class="left50"><i>Accentor modularis.</i></td> +</tr><tr> +<td class="left50"> +Wren</td> +<td class="left50"><i>Troglodytes troglodytes.</i></td> +</tr><tr> +<td class="left50"> +Spotted Flycatcher</td> +<td class="left50"><i>Muscicapa striata.</i></td> +</tr><tr> +<td class="left50"> +Swallow</td> +<td class="left50"><i>Hirundo rustica.</i></td> +</tr><tr> +<td class="left50"> +Martin</td> +<td class="left50"><i>Delichon urbica.</i></td> +</tr><tr> +<td class="left50"> +Sand-Martin</td> +<td class="left50"><i>Riparia riparia.</i></td> +</tr><tr> +<td class="left50"> +Great Spotted Woodpecker</td><td class="left50"><i>Dryobates major anglicus.</i></td> +</tr><tr> +<td class="left50"> +Lesser Spotted Woodpecker</td><td class="left50"><i>Dryobates minor.</i></td> +</tr><tr> +<td class="left50"> +Green Woodpecker</td><td class="left50"><i>Picus viridis.</i></td> +</tr><tr> +<td class="left50"> +Cuckoo</td><td class="left50"><i>Cuculus canorus.</i></td> +</tr><tr> +<td class="left50"> +Tawny Owl</td><td class="left50"><i>Strix aluco.</i></td> +</tr><tr> +<td class="left50"> +Buzzard</td><td class="left50"><i>Buteo buteo.</i></td> +</tr><tr> +<td class="left50"> +Sparrow-Hawk</td><td class="left50"><i>Accipiter nisus.</i></td> +</tr><tr> +<td class="left50"> +Peregrine Falcon</td><td class="left50"><i>Falco peregrinus.</i></td> +</tr><tr> +<td class="left50"> +Merlin</td><td class="left50"><i>Falco æsalon.</i></td> +</tr><tr> +<td class="left50"> +Kestrel</td><td class="left50"><i>Falco tinnunculus.</i></td> +</tr><tr> +<td class="left50"> +<span class='pagenum'><a name="Page_xiii" id="Page_xiii">xiii</a></span> +Shag</td><td class="left50"><i>Phalacrocorax graculus</i>.</td> +</tr><tr> +<td class="left50"> +Wild Duck</td><td class="left50"><i>Anas boschas</i>.</td> +</tr><tr> +<td class="left50"> +Snipe</td><td class="left50"><i>Gallinago gallinago</i>.</td> +</tr><tr> +<td class="left50"> +Dunlin</td><td class="left50"><i>Tringa alpina</i>.</td> +</tr><tr> +<td class="left50"> +Ruff</td><td class="left50"><i>Machetes pugnax</i>.</td> +</tr><tr> +<td class="left50"> +Redshank</td><td class="left50"><i>Totanus totanus</i>.</td> +</tr><tr> +<td class="left50"> +Black-tailed Godwit</td><td class="left50"><i>Limosa limosa</i>.</td> +</tr><tr> +<td class="left50"> +Curlew</td><td class="left50"><i>Numenius arquata</i>.</td> +</tr><tr> +<td class="left50"> +Whimbrel</td><td class="left50"><i>Numenius phæopus</i>.</td> +</tr><tr> +<td class="left50"> +American Golden Plover</td><td class="left50"><i>Charadrius dominicus</i>.</td> +</tr><tr> +<td class="left50"> +Lapwing</td><td class="left50"><i>Vanellus vanellus</i>.</td> +</tr><tr> +<td class="left50"> +Oyster-Catcher</td> +<td class="left50"><i>Hæmatopus ostralegus</i>.</td> +</tr><tr> +<td class="left50"> +Herring-Gull</td> +<td class="left50"><i>Larus argentatus</i>.</td> +</tr><tr> +<td class="left50"> +Kittiwake</td> +<td class="left50"><i>Rissa tridactyla</i>.</td> +</tr><tr> +<td class="left50"> +Razorbill</td><td class="left50"><i>Alca torda</i>.</td> +</tr><tr> +<td class="left50"> +Guillemot</td> +<td class="left50"><i>Uria troille</i>.</td> +</tr><tr> +<td class="left50"> +Puffin</td> +<td class="left50"><i>Fratercula arctica</i>.</td> +</tr><tr> +<td class="left50"> +Fulmar</td><td class="left50"><i>Fulmarus glacialis</i>.</td> +</tr><tr> +<td class="left50"> +Water-Rail</td><td class="left50"><i>Rallus aquaticus</i>.</td> +</tr><tr> +<td class="left50"> +Corn-Crake</td><td class="left50"><i>Crex crex</i>.</td> +</tr><tr> +<td class="left50"> +Moor-Hen</td> +<td class="left50"><i>Gallinula chloropus</i>.</td> +</tr><tr> +<td class="left50"> +Coot</td> +<td class="left50"><i>Fulica atra</i>.</td> +</tr><tr> +<td class="left50"> +Wood-Pigeon</td><td class="left50"><i>Columba palumbus</i>.</td> +</tr><tr> +<td class="left50"> +Turtle-Dove</td><td class="left50"><i>Streptopelia turtur</i>.</td> +</tr><tr> +<td class="left50"> +Partridge</td> +<td class="left50"><i>Perdix perdix</i>.</td> +</tr><tr> +<td class="left50"> +Black Grouse</td> +<td class="left50"><i>Lyrurus tetrix britannicus</i>.</td> +</tr><tr> +<td class="left50">Red Grouse</td> +<td class="left50"><i>Lagopus scoticus</i>.</td> +</tr> +</table> +<hr /> +<p><span class='pagenum'><a name="Page_1" id="Page_1">1</a></span></p> + +<h2>TERRITORY IN BIRD LIFE</h2> + +<h3>CHAPTER I</h3> + +<h4>INTRODUCTION</h4> + + +<p>In his <i>Manual of Psychology</i> Dr Stout reminds +us that "Human language is especially constructed +to describe the mental states of human +beings, and this means that it is especially +constructed so as to mislead us when we attempt +to describe the working of minds that differ in +a great degree from the human."</p> + +<p>The use of the word "territory" in connection +with the sexual life of birds is open to +the danger which we are here asked to guard +against, and I propose, therefore, before attempting +to establish the theory on general grounds, +to give some explanation of what the word is +intended to represent and some account of the +exact position that representation is supposed to +occupy in the drama of bird life.</p> + +<p>The word is capable of much expansion. +There cannot be territories without boundaries +of some description; there cannot well be +boundaries without disputes arising as to those +boundaries; nor, one would imagine, can there +be disputes without consciousness as a factor +entering into the situation; and so on, until by<span class='pagenum'><a name="Page_2" id="Page_2">2</a></span> +a simple mental process we conceive of a state +in bird life analogous to that which we know +to be customary amongst ourselves. Now, +although the term "breeding territory," when +applied to the sexual life of birds, is not altogether +a happy one, it is difficult to know +how otherwise to give expression to the facts +observed. Let it then be clearly understood that +the expression "securing a territory" is used to +denote a process, or rather part of a process, +which, in order to insure success to the individual +in the attainment of reproduction, has +been gradually evolved to meet the exigencies +of diverse circumstances. Regarded thus, we +avoid the risk of conceiving of the act of securing +a territory as a detached event in the life of a +bird, and avoid, I hope, the risk of a conception +based upon the meaning of the word when +used to describe human as opposed to animal +procedure.</p> + +<p>Success in the attainment of reproduction is +rightly considered to be the goal towards which +many processes in nature are tending. But +what is meant by success? Is it determined by +the actual discharge of the sexual function? +So many and so wonderful are the contrivances +which have slowly been evolved to insure this +discharge, that it is scarcely surprising to find +attention focused upon this one aspect of the +problem. Yet a moment's reflection will show +that so limited a definition of the term "success" +can only be held to apply to certain forms of +life; for where the young have to be cared for,<span class='pagenum'><a name="Page_3" id="Page_3">3</a></span> +fostered, and protected from molestation for +periods of varying lengths, the actual discharge +of the sexual function marks but one stage in a +process which can only succeed if all the contributory +factors adequately meet the essential +conditions of the continuance of the species.</p> + +<p>Securing a territory is then part of a process +which has for its goal the successful rearing +of offspring. In this process the functioning +of the primary impulse, the acquirement of a +place suitable for breeding purposes, the advent +of a female, the discharge of the sexual function, +the construction of the nest, and the +rearing of offspring follow one another in +orderly sequence. But since we know so little +of the organic changes which determine sexual +behaviour, and have no means of ascertaining +the nature of the impulse which is first +aroused, we can only deal with the situation +from the point at which the internal organic +changes reflect themselves in the behaviour to +a degree which is visible to an external observer. +That point is reached when large numbers of +species, forsaking the normal routine of existence +to which they have been accustomed for +some months, suddenly adopt a radical change +in their mode of behaviour. How is this change +made known to us? By vast numbers of +individuals hurrying from one part of the globe +to another, from one country to another, and +even from mid-ocean to the coasts; by detachments +travelling from one district to another; +by isolated individuals deserting this place for<span class='pagenum'><a name="Page_4" id="Page_4">4</a></span> +that; by all those movements, in fact, which +the term migration, widely applied, is held to +denote. Now the impulse which prompts these +travelling hosts must be similar in kind whether +the journey be long or short; and it were better, +one would think, to regard such movements as +a whole than to fix the attention on some one +particular journey which fills us with amazement +on account of the magnitude of the distance +traversed or the nature of the difficulties overcome. +For, after all, what does each individual +seek? There may be some immature birds which, +though they have not reached the necessary +stage of development, happen to fall in with +others in whom the impulse is strong and are +led by them—they know not where. But the +majority seek neither continent nor country, +neither district nor locality is their aim, but a +place wherein the rearing of offspring can be +safely accomplished; and the search for this +place is the earliest visible manifestation in many +species of the reawakening of the sexual instinct.</p> + +<p>The movements of each individual are then +directed towards a similar goal, namely, the +occupation of a definite station; and this +involves for many species a distinct change in +the routine of behaviour to which previously they +had been accustomed. Observe, for example, +one of the numerous flocks of Finches that +roam about the fields throughout the winter. +Though it may be composed of large numbers +of individuals of different kinds, yet the various +units form an amicable society actuated by<span class='pagenum'><a name="Page_5" id="Page_5">5</a></span> +one motive—the procuring of food. And since +it is to the advantage of all that the individual +should be subordinated to the welfare +of the community as a whole there is no dissension, +apart from an occasional quarrel here +and there.</p> + +<p>In response, however, to some internal organic +change, which occurs early in the season, +individuality emerges as a factor in the developing +situation, and one by one the males betake +themselves to secluded positions, where each +one, occupying a limited area, isolates itself from +companions. Thereafter we no longer find that +certain fields are tenanted by flocks of greater +or less dimensions, while acres of land are +uninhabited, but we observe that the hedgerows +and thickets are divided up into so many territories, +each one of which contains its owner. +This procedure, with of course varying detail, +is typical of that of many species that breed in +Western Europe. And since such a radical +departure from the normal routine of behaviour +could scarcely appear generation after generation +in so many widely divergent forms, and still be +so uniform in occurrence each returning season, +if it were not founded upon some congenital +basis, it is probable that the journey, whether it +be the extensive one of the Warbler or the short +one of the Reed-Bunting, is undertaken in +response to some inherited disposition, and +probable also that the disposition bears some +relation to the few acres in which the bird +ultimately finds a resting place. Whilst for<span class='pagenum'><a name="Page_6" id="Page_6">6</a></span> +the purpose of the theory I shall give expression +to this behaviour in terms of that +theory, and speak of it as a disposition to +secure a territory, using the word disposition, +which has been rendered current in recent discussion, +for that part of the inherited nature +which has been organised to subserve a specific +biological purpose—strict compliance with the +rules of psychological analysis requires a simpler +definition; let us therefore say "disposition to +remain in a particular place in a particular +environment."</p> + +<p>But even granting that this disposition +forms part of the hereditary equipment of +the bird, how is the process of reproduction +furthered? The mere fact of remaining in or +about a particular spot cannot render the attainment +of reproduction any less arduous, and may +indeed add to the difficulties, for any number +of individuals might congregate together and +mutually affect one another's interests. A +second disposition comes, however, into functional +activity at much the same stage of sexual +development, and manifests itself in the male's +intolerance of other individuals. And the two +combined open up an avenue through which +the individual can approach the goal of reproduction. +In terms of the theory I shall +refer to this second disposition as the one +which is concerned with the defence of the +territory.</p> + +<p>Broadly speaking, these two dispositions may +be regarded as the basis upon which the breed<span class='pagenum'><a name="Page_7" id="Page_7">7</a></span>ing +territory is founded. Yet inasmuch as the +survival value of the dispositions themselves +must have depended upon the success of the +process as a whole, it is manifest that peculiar +significance must not be attached to just the +area occupied, which happens to be so susceptible +of observation; other contributory factors +must also receive attention, for the process is +but an order of relationships in which the +various units have each had their share in +determining the nature and course of subsequent +process, so that, as Dr Stout says, when they +were modified, it was modified.</p> + +<p>Now the male inherits a disposition which +leads it to remain in a restricted area, but the +disposition cannot determine the extent of that +area. How then are the boundaries fixed? +That they are sometimes adhered to with +remarkable precision, that they can only be +encroached upon at the risk of a conflict—all of +this can be observed with little difficulty. But +if we regard them as so many lines definitely +delimiting an area of which the bird is cognisant, +we place the whole behaviour on a different +level of mental development, and incidentally +alter the complexion of the whole process. It +would be a mistake, I think, to do this. Though +conscious intention as a factor may enter the +situation, there is no necessity for it to do so; +there is no necessity, that is to say, for the bird +to form a mental image of the area to be +occupied and shape its course accordingly. The +same result can be obtained without our having<span class='pagenum'><a name="Page_8" id="Page_8">8</a></span> +recourse to so complex a principle of explanation, +and that by the law of habit formation. +In common with other animals, birds are +subject to this law in a marked degree. An +acquired mode of activity becomes by repetition +ingrained in the life of the individual, so that +an action performed to-day is liable to be +repeated to-morrow so long as it does not prejudice +the existence or annul the fertility of the +individual.</p> + +<p>Let us see how this may have operated in +determining the limits of the area acquired, and +for this purpose let us suppose that we are +observing a male Reed-Bunting recently established +in some secluded piece of marsh land. +Scattered about this particular marsh are a +number of small willows and young alder trees, +each one of which is capable of providing plenty +of branches suitable for the bird to perch upon, +and all are in a like favourable position so far as +the outlook therefrom is concerned. Well, we +should expect to find that each respective tree +would be made use of according to the position +in which the bird happened to find itself. But +what actually do we find—one tree singled out +and resorted to with ever-increasing certainty +until it becomes an important point in relation +to the occupied area, a headquarters from +which the bird advertises its presence by song, +keeps watch upon the movements of its +neighbours, and sets out for the purpose of +securing food. We then take note of its +wanderings in the immediate vicinity of the<span class='pagenum'><a name="Page_9" id="Page_9">9</a></span> +headquarters, especially as regards the direction, +frequency, and extent of the journeys; and +we discover not only that these journeys proceed +from and terminate in the special tree, +but that there is a sameness about the actual +path that is followed. The bird takes a short +flight, searches a bush here and some rushes +there, returns, and after a while repeats the +performance; we on our part mark the extreme +limits reached in each direction, and by continued +observation discover that these limits +are seldom exceeded, that definition grows more +and more pronounced, and that by degrees +the movements of the bird are confined within +a restricted area. In outline, this is what +happens in a host of cases. By repetition +certain performances become stereotyped, certain +paths fixed, and a routine is thus established +which becomes increasingly definite as +the season advances.</p> + +<p>But while it would be quite untrue to say +that this routine is never departed from, and +equally profitless to attempt to find a point +beyond which the bird will under no circumstances +wander, yet there is enough definition +and more than enough to answer the purpose +for which the territory has, I believe, been +evolved, that is to say the biological end of +reproduction. Again, however, the process of +adjustment is a complex one. Habit plays its +part in determining the boundaries in a rough +and ready manner, but the congenital basis, +which is to be found in the behaviour adapted<span class='pagenum'><a name="Page_10" id="Page_10">10</a></span> +to a particular environment, is an important +factor in the situation. For example, if instead +of resting content with just a bare position +sufficient for the purpose of reproduction, the +Guillemot were to hustle its neighbours from +adjoining ledges, the Guillemot as a species +would probably disappear; or if instead of +securing an area capable of supplying sufficient +food both for itself and its young, the Chiffchaff +were to confine itself to a single tree, and, +after the manner of the Guillemot, trust to +spasmodic excursions into neutral ground for +the purpose of obtaining food, the Chiffchaff as +a species would probably not endure. All such +adjustments have, however, been brought about +by relationships which have gradually become +interwoven in the tissue of the race.</p> + +<p>The intolerance that the male displays +towards other individuals, usually of the same +sex, leads to a vast amount of strife. Nowhere +in the animal world are conflicts more frequent, +more prolonged, and more determined than in +the sexual life of birds; and though they are +acknowledged to be an important factor in the +life of the individual, yet there is much difference +of opinion as to the exact position they +occupy in the drama of bird life. Partly +because they frequently happen to be in +evidence, partly because they are numerically +inferior, and partly, I suppose, because the +competition thus created would be a means of +maintaining efficiency, the females, by common +consent, are supposed to supply the condition<span class='pagenum'><a name="Page_11" id="Page_11">11</a></span> +under which the pugnacious nature of the +male is rendered susceptible to appropriate +stimulation. And so long as the evidence +seemed to show that battles were confined +to the male sex, so long were there grounds +for hoping that their origin might be traced +to such competition. But female fights with +female, pair with pair, and, which is still +more remarkable, a pair will attack a single +male or a single female; moreover, males that +reach their destination in advance of their +prospective mates engage in serious warfare. +How then is it possible to look upon the +individuals of one sex as directly responsible for +the strife amongst those of the other, or how +can the female supply the necessary condition? +As long as an attempt is made to explain it in +terms of the female, the fighting will appear to +be of a confused order; regard it, however, as part +of a larger process which demands, amongst +other essential conditions of the breeding +situation, the occupation of a definite territory, +and order will reign in place of confusion.</p> + +<p>But even supposing that the male inherits +a disposition to acquire a suitable area, even +supposing that it inherits a disposition which +results indirectly in the defence of that area, +how does it obtain a mate? If the female +behaved in a like manner, if she, too, were to +isolate herself and remain in one place definitely, +that would only add to the difficulties of mutual +discovery. We find, however, in the migrants, +that the males are earlier than the females<span class='pagenum'><a name="Page_12" id="Page_12">12</a></span> +in reaching the breeding grounds, and, in +resident species, that they desert the females +and retire alone to their prospective territories, +so that there is a difference in the behaviour +of the sexes at the very commencement of +the sexual process. What is the immediate +consequence? Since the male isolates itself, +it follows, if the union of the sexes is to be +effected, that the discovery of a mate must +rest largely with the female. This of course +reverses the accepted course of procedure. +But after all, what reason is there to suppose +that, the male seeks the female, or that a +mutual search takes place; what reason to +think that this part of the process is subject +to no control except such as may be supplied +by the laws of chance?</p> + +<p>Now, clearly, much will depend upon the +rapidity with which the female can discover a +male fit to breed; for if the course of reproduction +is to flow smoothly, there must be neither +undue delay nor waste of energy incurred in the +search—some guidance is therefore necessary, +some control in her external environment. +Here the song, or the mechanically produced +sound, comes into play, and assists in the attainment +of this end. Nevertheless if every male +were to make use of its powers whether it were +in occupation of a territory or not, if the +wandering individual had an equal chance of +attracting a mate, then it would be idle to +attempt to establish any relation between +"song" on the one hand, and "territory" on<span class='pagenum'><a name="Page_13" id="Page_13">13</a></span> +the other, and impossible to regard the voice as +the medium through which an effectual union of +the sexes is procured. But there is reason to +believe that the males utilise their powers of +producing sound only under certain well-defined +conditions. For instance, when they are on +their way to the breeding grounds, or moving +from locality to locality in search of isolation, or +when they desert their territories temporarily, +as certain of the residents often do, they are +generally silent; but when they are in occupation +of their territories they become vociferous—and +this is notoriously the case during the +early hours of the day, which is the period of +maximum activity so far as sexual behaviour is +concerned. So that just at the moment when +the sexual impulse of the female is most susceptible +to stimulation, the males are betraying +their positions and are thus a guide to her +movements. Nevertheless, even though she +may have discovered a male ready to breed, +success is not necessarily assured to her; for +with multitudes of individuals striving to procreate +their kind, it would be surprising if there +were no clashing of interests, if no two females +were ever to meet in the same occupied territory. +Competition of this kind is not uncommon, and +the final appeal is to the law of battle, just as an +appeal to physical strength sometimes decides +the question of the initial ownership of a +territory.</p> + +<p>I shall try to make clear the relations +of the various parts to the whole with the<span class='pagenum'><a name="Page_14" id="Page_14">14</a></span> +assistance of whatever facts I can command. +I shall do so not only for the purposes of the +theory, but because one so often finds the +more important features of sexual behaviour +regarded as so many distinct phenomena requiring +separate treatment, whereas they are mutually +dependent, and follow one another in ordered +sequence. I spoke of the process as a series +of relationships. Some of these relationships +have already been touched upon; others will +become apparent if we consider for a moment +the purposes for which the territory has been +evolved. Indirectly its purpose is that of the +whole process, the rearing of offspring. But +inasmuch as a certain measure of success could +be attained, and that perhaps often, without all +the complications introduced by the territory, +there are manifestly advantages to be gained +by its inclusion in the scheme. The difficulties +which beset the path of reproduction are by no +means always the same—all manner of adjustments +have to be made to suit the needs of +different species. There are direct relationships, +such as we have been speaking of, which are +essential to the every-day working of the +process, and others which are indirect, though +none the less important for they must have +exercised an influence throughout the ages. +These latter are furnished by the physical—the +inorganic world, by climate, by the supply of +the particular kind of breeding stations, by the +scarcity or abundance of the necessary food +and by the relative position of the food supply<span class='pagenum'><a name="Page_15" id="Page_15">15</a></span> +to the places suitable for breeding. Why does +the Reed-Bunting cling so tenaciously to an +acre or more of marshy ground, while the +Guillemot rests content with a few square feet +on a particular ledge of rock? The answer is +the same in both cases—to facilitate reproduction. +But why should a small bird require +so many square yards, whilst a very much +larger one is satisfied with so small an area? +The explanation must be sought in the conditions +of existence. The Reed-Bunting has +no difficulty in finding a position suitable for +the construction of its nest; there are acres +of waste land and reedy swamps capable of +supplying food for large numbers of individuals, +and the necessary situations for countless nests. +But its young, like those of many another +species, are born in a very helpless state. For +all practical purposes they are without covering +of any description and consequently require +protection from the elements, warmth from +the body of the brooding bird, and repeated +supplies of nourishment. A threefold burden +is thus imposed upon the parents: they must +find food for themselves, they must afford +protection to the young by brooding, and they +must supply them with the necessary food at +regular intervals. And their ability to do all +this that is demanded of them will be severely +taxed by the brooding which must perforce +curtail the time available for the collection +of food.</p> + +<p>Let us then suppose that the Reed-Buntings<span class='pagenum'><a name="Page_16" id="Page_16">16</a></span> +inhabiting a certain piece of marsh are divided +into two classes, those which are pugnacious +and intolerant of the approach of strangers, and +those which welcome their presence. The nests +of the former will be built in isolation, those +of the latter in close proximity. In due course +eggs will be laid and incubation performed, +and thus far all alike will probably be successful. +Here, however, a critical point is reached. If +the young are to be freed from the risk of +exposure, the parents must find the necessary +supply of food rapidly. But manifestly all +will not be in a like satisfactory position to +accomplish this, for whereas the isolated pairs +will have free access to all the food in the +immediate vicinity of the nest, those which +have built in proximity to one another, meeting +competition in every direction, will be compelled +to roam farther afield and waste much +valuable time by doing so; and under conditions +which can well be imagined, even this slight +loss of time will be sufficient to impede the +growth of the delicate offspring, or to lead +perhaps to still greater disaster. If any one +doubts this, let him first examine one of the +fragile offspring; let him then study the conditions +under which it is reared, observing the +proportion of time it passes in sleep and the +anxiety of the parent bird to brood; and finally +let him picture to himself its plight in a wet +season if, in order to collect the necessary food, +the parents were obliged to absent themselves +for periods of long duration.</p> + +<p><span class='pagenum'><a name="Page_17" id="Page_17">17</a></span>Now take the case of the Guillemot. Its +young at birth are by no means helpless in the +sense that the young Reed-Bunting is, and food +is readily procured. But breeding stations are +scarce, for although there are many miles of +cliff-bound coast, yet not every type of rock +formation produces the fissures and ledges upon +which the bird rests. Hence vast stretches of +coast-line remain uninhabited, and the birds are +forced to concentrate at certain points, where +year after year they assemble in countless +numbers from distant parts of the ocean. If, +then, different individuals were to jostle one +another from adjoining positions, and each one +were to attempt to occupy a ledge in solitary +State, not only would the successful ones gain +no advantage from the additional space over +which they exercised dominion, but inasmuch as +many members that were fitted to breed would +be precluded from doing so, the status of the +species as a whole would be seriously affected. +The amount of space occupied by each individual +is therefore a matter of urgent importance. A +few square feet of rock sufficient for the immediate +purpose of incubation is all that can be +allowed if the species is to maintain its position +in the struggle for existence.</p> + +<p>Our difficulty in estimating the importance +of the various factors that make for success or +failure arises from our inability to see more than +a small part of the scene as it slowly unfolds +itself. The peculiar circumstances under which +these cliff-breeding forms dwell does, however,<span class='pagenum'><a name="Page_18" id="Page_18">18</a></span> +enable us to picture, on the one hand, the +precarious situation of an individual that was +incapable of winning or holding a position at +the accustomed breeding station, and, on the +other, the plight of the species as a whole if +each one exercised authority over too large an +area. With the majority of species it is difficult +to do this. So many square miles of suitable +breeding ground are inhabited by so few Reed-Buntings +that, even supposing certain members +were to establish an ascendency over too wide +an area, it would be impossible to discover +by actual observation whether the race as a +whole were being adversely affected. Competition +doubtless varies at different periods and +in different districts according to the numerical +standing of the species in a given locality and +according to the numerical standing of others +that require similar conditions of existence; at +times it may even be absent, just as at any +moment it may become acute. These examples +show how profoundly the evolution of the +breeding territory may have been influenced by +relationships in the inorganic world, and they +give some idea of the intricate nature of the +problem with which we have to deal.</p> + +<p>I mentioned that the first visible manifestation +of the revival of the sexual instinct +was to be found in the movements undertaken +by the males at the commencement +of the breeding season. Such movements are +characterised by a definiteness of purpose, +whether they involve a protracted journey of<span class='pagenum'><a name="Page_19" id="Page_19">19</a></span> +some hundreds of miles or merely embrace a +parish or so in extent, and that purpose is the +acquirement of a territory suitable for rearing +offspring. They are thus directly related to the +territory, and the question arises as to whether +their origin may not be traced to such relatedness. +So long as we fix our attention solely +upon the magnitude of the distance traversed +the suggestion may seem a fanciful one. Nevertheless, +if the battles between males of the +same species <i>are</i> directly related to the occupation +of a position suitable for breeding purposes, +if those which occur between males of closely +related forms <i>can</i> be traced to a similar source, +if the females take their share in the defence +of the ground that is occupied, if, in short, the +competition is as severe as I believe it to be, +and is wholly responsible for the strife which +is prevalent at the commencement of the +breeding season—then such competition must +have introduced profound modifications in the +distribution of species; it must have even +influenced the question of the survival of +certain forms and the elimination of others; +and since the powers of locomotion of a bird +are so highly developed it must have led to +an extension of breeding range, limited only +by unfavourable conditions of existence.</p> +<hr /> +<p><span class='pagenum'><a name="Page_20" id="Page_20">20</a></span></p> +<h3>CHAPTER II</h3> + +<h4>THE DISPOSITION TO SECURE A TERRITORY</h4> + + +<p>Those who have studied bird life throughout +the year are aware that the distribution of +individuals changes with the changing seasons. +During autumn and winter, food is not so +plentiful and can only be found in certain places, +and so, partly by force of circumstances and +partly on account of the gregarious instinct +which then comes into functional activity, +different individuals are drawn together and +form flocks of greater or less dimensions, which +come and go according to the prevailing climatic +conditions. But with the advent of spring a +change comes over the scene: flocks disperse, +family parties break up, summer migrants begin +to arrive, and the hedgerows and plantations are +suddenly quickened into life. The silence of +the winter is broken by an outburst of song +from the throats of many different species, and +individuals appear in their old haunts and vie +with one another in advertising their presence +by the aid of whatever vocal powers they +happen to possess—the Woodpecker utters its +monotonous call from the accustomed oak; the<span class='pagenum'><a name="Page_21" id="Page_21">21</a></span> +Missel-Thrush, perched upon the topmost +branches of the elm, persistently repeats its few +wild notes; and the Swallow returns to the barn.</p> + +<p>All of this we observe each season, and our +thoughts probably travel to the delicate piece of +architecture in the undergrowth, or to the hole +excavated with such skill in the tree trunk; to +the beautifully shaped eggs; to the parent birds +carrying out their work with devoted zeal—in +fact, to the whole series of events which complete +the sexual life of the individual; and the attachment +of a particular bird to a particular spot is +readily accounted for in terms of one or other +of the emotions which centre round the human +home.</p> + +<p>But if this behaviour is to be understood +aright; if, that is to say, the exact position it +occupies in the drama of bird life is to be +properly determined, and its biological significance +estimated at its true value, it is above all +things necessary to refrain from appealing to +any one of the emotions which we are accustomed +to associate with ourselves, unless our +ground for doing so is more than ordinarily +secure. I shall try to show that, in the case of +many species, the male inherits a disposition to +secure a territory; or, inasmuch as the word +"secure" carries with it too much prospective +meaning, a disposition to remain in a particular +place when the appropriate time arrives.</p> + +<p>If the part which the breeding territory +plays in the sexual life of birds is the important +one I believe it to be, it follows that the<span class='pagenum'><a name="Page_22" id="Page_22">22</a></span> +necessary physiological condition must arise at +an early stage in the cycle of events which +follow one another in ordered sequence and +make towards the goal of reproduction, and that +the behaviour to which it leads must be one of +the earliest visible manifestations of the seasonal +development of the sexual instinct. When does +this seasonal development occur? For how +long does the instinct lie dormant? In some +species there is evidence of this first step in the +process of reproduction early in February; there +is reason to believe that in others the latter part +of January is the period of revival; and the +possibility must not be overlooked of still earlier +awakenings, marked with little definiteness, +though nevertheless of sufficient strength to call +into functional activity the primary impulse in +the sexual cycle. Here, then, we meet with a +difficulty so far as direct observation is concerned, +for the duration of the period of +dormancy and the precise date of revival vary +in different species; and, if accurate information +is to be obtained, the study of the series of +events which culminate in the attainment +of reproduction ought certainly to begin the +moment behaviour is influenced by the internal +changes, whatever they may be, which are +responsible for the awakening of the sexual +instinct.</p> + +<p>In considering how this difficulty might be +met, the importance of migratory species as a +channel of information was gradually borne in +upon me; for it seemed that the definiteness<span class='pagenum'><a name="Page_23" id="Page_23">23</a></span> +with which the initial stage in the sexual process +was marked off, as a result of the incidence of +migration, would go far towards removing much +of the obscurity which appeared to surround the +earlier stages of the breeding problem in the +case of resident species. Recent observation +has shown that I exaggerated this difficulty, and +that it is generally possible to determine with +reasonable accuracy the approximate date at +which the internal changes begin to exert an +influence on the behaviour of resident species +also. Nevertheless, the specialised behaviour of +the migrants furnished a clue, and pointed out +the direction which further inquiry ought to +take.</p> + +<p>Those who are accustomed to notice the +arrival of the migrants are aware that the woods, +thickets, and marshes do not suddenly become +occupied by large numbers of individuals, but +that the process of "filling up" is a gradual +one. An individual appears here, another there; +then after a pause there is a further addition, +and so on with increasing volume until the tide +reaches its maximum, then activity wanes, and +the slowly decreasing number of fresh arrivals +passes unnoticed in the wealth of new life that +everywhere forces itself upon our attention. If +now, instead of surveying the migrants as a +whole, our attention be directed to one species +only, this gradual arrival of single individuals in +their accustomed haunts will become even more +apparent; and if the investigation be pursued +still further and these single individuals observed<span class='pagenum'><a name="Page_24" id="Page_24">24</a></span> +more closely, it will be found that in nearly +every case they belong to the male sex. Males +therefore arrive before females. This does not +mean, however, that the respective times of +arrival of the males and females belonging to +any one species are definitely divided, for males +continue to arrive even after some of the females +have reached their destination; and thus a certain +amount of overlapping occurs. A truer +definition of the order of migration would be as +follows:—Some males arrive before others, and +some females arrive before others, but on the +average males arrive before females. This fact +has long been known. Gätke refers to it in his +<i>Birds of Heligoland</i>. "Here in Heligoland," he +says, "the forerunners of the spring migration +are invariably old males; a week or two later, +solitary old females make their appearance; and +after several weeks, both sexes occur mixed, <i>i.e.</i>, +females and younger males; while finally only +young birds of the previous year are met with." +Newton alludes to it as follows:—"It has been +ascertained by repeated observation that in the +spring movement of most species of the northern +hemisphere, the cock birds are always in the van +of the advancing army, and that they appear some +days, or perhaps weeks, before the hens"; and +Dr Eagle Clarke, in his <i>Studies in Bird Migration</i>, +makes the following statement:—"Another +characteristic of the spring is that the males, +the more ardent suitors, of most species, travel +in advance of the females, and arrive at their +meeting quarters some days, it is said in some<span class='pagenum'><a name="Page_25" id="Page_25">25</a></span> +cases even weeks, before their consorts." Some +interesting details were given in <i>British Birds</i><a name="FNanchor_1_1" id="FNanchor_1_1"></a><a href="#Footnote_1_1" class="fnanchor">1</a> +in regard to the sex of the migrants that were +killed by striking the lantern at the Tuskar +Rock, Co. Wexford, on the 30th April 1914. In +all, there were twenty-four Whitethroats, nine +Willow-Warblers, eight Sedge-Warblers, and six +Wheatears; and on dissection it was found that +twenty Whitethroats, seven Willow-Warblers, +eight Sedge-Warblers, and one Wheatear were +males.</p> + +<p>What a curious departure this seems from +the usual custom in the animal world! Here +we have the spectacle afforded us of the males, +in whom presumably the sexual instinct has +awakened, deserting the females just at the +moment when we might reasonably expect their +impulse to accompany them would be strongest; +and this because of their inherited disposition +to reach the breeding grounds. If, in order +to attain to reproduction, the male depended +primarily upon securing a female—whether by +winning or fighting matters not at the moment—if +her possession constituted the sole difference +in his external environment between success and +failure, then surely one would suppose that an +advantage must rest with those individuals +which, instead of rushing forward and inflicting +upon themselves a life of temporary isolation, +remained with the females and increased +their opportunities for developing that mutual +appreciation which, by some, is held to be a +<span class='pagenum'><a name="Page_26" id="Page_26">26</a></span> +necessary prelude to the completion of the +sexual act, and to which close companionship +would tend to impart a stimulus.</p> + +<p>In thus speaking, however, we assume that +the revival of the sexual instinct in the migratory +male is coincident in time with its return to the +breeding quarters; and we do so because the +act of migrating is believed to be the first step +in the breeding process. But it is well to bear in +mind just how much of this assumption is based +upon fact, and how much is due to questionable +inference. All that can be definitely asserted is +this, that appropriate dissection reveals in most +of the migrants, upon arrival at their destination, +unquestionable evidence of seasonal increase in +the size of the sexual organs. Beyond this there +is nothing to go upon. Yet if the term "sexual +instinct" is held to comprise the whole series of +complex relationships which are manifest to us +in numerous and specialised modes of behaviour, +which ultimately lead to reproduction, and which +have gradually become interwoven in the tissue +of the race, there can be little doubt that the +assumption is a reasonable one. To some, the +term may recall the fierce conflicts which are +characteristic of the season; to others, emotional +response; to not a few, perhaps, the actual +discharge of the sexual function—all of these, it +is true, are different aspects of the one instinct; +but at the same time each one marks a stage in +the process, and the different stages follow one +another in ordered sequence. However, we are +not concerned at the moment with the term in<span class='pagenum'><a name="Page_27" id="Page_27">27</a></span> +its wider application; we wish to know the +precise stage at which the disposition to mate +influences the behaviour of the male. Is the +female to him, from the moment the seasonal +change in his sexual organs takes place, a goal +that at all costs must be attained? Or is it only +when the cycle of events which leads up to +reproduction is nearing completion that she +looms upon his horizon? One would like to be +in a position to answer these questions, but +there is nothing in the way of experimental +evidence to go upon; and if I say that there is +reason to believe that, in the earlier stages, the +female is but a shadow in the external environment +of the male, it must be taken merely as +an expression of opinion, though based in some +measure upon a general observation of the +behaviour of various species.</p> + +<p>Before attempting to explain the difference +in the times of arrival of the male and female +migrant, let us examine the behaviour of some +resident species at a corresponding period. +My investigations have been made principally +amongst the smaller species—the Finches and +the Buntings—which often pass the winter in +or near the localities wherein they brought up +offspring or were reared. It is true that they +wander from one field to another according to +the abundance or scarcity of food; it is also true +that, if the weather is of a type which precludes +the possibility of finding the necessary food, +these wanderings may become extensive or even +develop into partial migrations. But under the<span class='pagenum'><a name="Page_28" id="Page_28">28</a></span> +normal climatic conditions which prevail in +many parts of Britain, these smaller resident +species seem to find all that they require +without travelling any great distance from +their breeding haunts. Flocks composed of +Yellow Buntings, Cirl Buntings, Corn-Buntings, +Chaffinches, Greenfinches, etc., can be observed +round the farmsteads or upon arable land; small +flocks of Reed-Buntings take up their abode on +pieces of waste land and remain there until the +supply of food is exhausted, deserting their +feeding ground only towards evening when +they retire to the nearest reed-bed to pass the +night; flocks of Hawfinches visit the same holly-trees +day after day so long as there is an +abundance of berries on the ground beneath; +and so on.</p> + +<p>I have mentioned the Reed-Bunting; let us +take it as our first example and try to follow its +movements when the influence exerted by the +internal secretions begins to be reflected on the +course of its behaviour. First, it will be +necessary to discover the exact localities in any +given district to which the species habitually +returns for the purpose of procreation; otherwise +the earlier symptoms of any disposition to +secure a territory may quite possibly be overlooked +in the search for its breeding haunts.</p> + +<p>In open weather Reed-Buntings pass the +winter either singly, in twos or threes, or in +small flocks, on bare arable ground, upon seed +fields, or in the vicinity of water-courses; but +in the breeding season they resort to marshy<span class='pagenum'><a name="Page_29" id="Page_29">29</a></span> +ground where the <i>Juncus communis</i> grows in +abundance, to the dense masses of the common +reed (<i>Arundo phragmites</i>), and such like places. +During the winter, the male's routine of existence +is of a somewhat monotonous order, limited +to the necessary search for food during the few +short hours of daylight and enforced inactivity +during the longer hours of darkness. But +towards the middle of February a distinct +change manifests itself in the bird's behaviour. +Observe what then happens. When they leave +the reed-bed in the morning, instead of flying +with their companions to the accustomed feeding +grounds, the males isolate themselves and scatter +in different directions. The purpose of their +behaviour is not, however, to find fresh feeding +grounds, nor even to search for food as they +have been wont to do, but rather to discover +stations suitable for the purpose of breeding; +and, having done so, each male behaves in a +like manner—it selects some willow, alder, or +prominent reed, and, perching thereon, leads +a quiet life, singing or preening its feathers. +Now if the movements of one particular male +are kept in view, it will be noticed that only +part of its time is spent in its territory. At +intervals it disappears. I do not mean that one +merely loses sight of it, but that it actually +deserts its territory. As if seized with a sudden +impulse it rises into the air and flies away, often +for a considerable distance and often in the same +direction, and is absent for a period which may +vary in length from a few minutes to an hour<span class='pagenum'><a name="Page_30" id="Page_30">30</a></span> +or even more. But these periodical desertions +become progressively less and less frequent in +occurrence until the whole of its life is spent +in the few acres in which it has established +itself.</p> + +<p>The behaviour of the Yellow Bunting is +similar. In any roadside hedge two or more +males can generally be found within a short +distance of one another, and in such a place +their movements can be closely and conveniently +followed. Under normal conditions the ordinary +winter routine continues until early in February; +but the male then deserts the flock, seeks a +position of its own, and becomes isolated from +its companions. Now the position which it +selects does not, as a rule, embrace a very large +area—a few acres perhaps at the most. But +there is always some one point which is singled +out and resorted to with marked frequency—a +tree, a bush, a gate-post, a railing, anything in +fact which can form a convenient perch, and +eventually it becomes a central part of the +bird's environment. Here it spends the greater +part of its time, here it utters its song persistently, +and here it keeps watch upon intruders. The +process of establishment is nevertheless a +gradual one. The male does not appear in its +few acres suddenly and remain there permanently +as does the migrant; at first it may not even +roost in the prospective territory. The course +of procedure is somewhat as follows:—At dawn +it arrives and for a while utters its song, preens +its feathers, or searches for food; then it vanishes,<span class='pagenum'><a name="Page_31" id="Page_31">31</a></span> +rising into the air and flying in one fixed +direction as far as the eye can follow, until +it becomes a speck upon the horizon and is +ultimately lost to view. During these excursions +it rejoins the small composite flocks which still +frequent the fields and farm buildings. For a +time the hedgerow is deserted and the bird +remains with its companions. But one does not +have to wait long for the return; it reappears +as suddenly as it vanished, flying straight back +to the few acres which constitute its territory, +back even to the same gate-post or railing, +where it again sings. This simple routine may +be repeated quite a number of times during the +first two hours or so of daylight, with, of course, +a certain amount of variation; on one occasion +the bird may be away for a few minutes only, +on another for perhaps half an hour, whilst +sometimes it will fly for a few hundred yards, +hesitate, and then return—all of which shows +clearly enough that these few acres possess +some peculiar significance and are capable of +exercising a powerful influence upon the course +of its behaviour. And so the disposition in +relation to the territory becomes dominant in +the life of the bird.</p> + +<p>Or take the case of the Chaffinch. In +winter large or small flocks can be found in +many varied situations. But in the latter part +of February, or the early days of March, these +flocks begin to disperse. At daylight males +can then be observed in all kinds of situations, +either calling loudly, uttering their spring note,<span class='pagenum'><a name="Page_32" id="Page_32">32</a></span> +or exercising their vocal powers to the full; +and it will be found that, in the majority of +instances, these males are solitary individuals, +that they pass the early hours of the morning +alone, and that their normal routine of calling, +singing, or searching for food, is only interrupted +by quarrels with their neighbours. The same +locality is visited regularly—not only the same +acre or so of ground, but even the same elm +or oak, has, as its daily occupant, the same cock +Chaffinch. And temporary desertions from the +territory occur also, much like those referred to +in the life of the Bunting, but perhaps not so +frequently. One has grown so accustomed +during the dark days of winter to the sociable +side of Chaffinch behaviour—to the large flocks +searching for food, to the endless stream of +individuals returning in the evening to roost +in the holly-trees, to the absence of song—that +this radical departure from the normal +routine comes as something of a surprise; for +the days are still short, the temperature is still +low, the nesting season is still many weeks +ahead, and yet for part of the day, and for just +that part when the promptings of hunger must +be strongest, the male, instead of joining the +flock, isolates itself and expends a good deal of +energy in insuring that its isolation shall be +complete. And in place of the silence we +hear from all directions the cheerful song +uttered with such marked persistency that it +almost seems as if the bird itself must be +aware that by doing so it was advertising the<span class='pagenum'><a name="Page_33" id="Page_33">33</a></span> +fact of its occupation of a territory. This +is surely a remarkable change, and the females +in the meantime continue their winter routine.</p> + +<p>One other example. The monotonous call +of the Greenfinch is probably familiar to all. +In winter these birds accompany other Finches +and form with them flocks of varying sizes, but +in the spring the flocks disperse, and the Greenfinch, +in common with other units of the flock, +alters its mode of life. But whereas the +Chaffinch or the Bunting begins to acquire +its territory in February, the Greenfinch only +does so in April. When the organic changes +do at length begin to make themselves felt, +the male seeks a position of its own, and +having found one remains there, uttering its +characteristic call. But owing probably to the +fact that it is much later than the aforementioned +species in acquiring a territory, +temporary desertions are not so much in evidence. +The species is so very plentiful, and +the bird is so prone to nest in gardens and +shrubberies surrounding human habitations, that +this seasonal change in its routine of existence +cannot fail to be noticed. One can hear its +call in every direction, one can watch the +same individual in the same tree; and it is +the male that is thus seen and heard, the +female appears later. Thus the behaviour falls +into line with that of the Bunting or the +Chaffinch.</p> + +<p>The behaviour of these resident species +throws some light upon the early arrival of the<span class='pagenum'><a name="Page_34" id="Page_34">34</a></span> +males which we are endeavouring to explain in +the case of the migrants. Let us see how their +actions compare. The male resident deserts the +female early in the year and establishes itself in +a definite position, where it advertises its presence +by song; the male migrant travels from a great +distance, arrives later, and also establishes itself +in a definite position, where it, too, advertises its +presence by song. The male resident passes +only the earlier part of the day in its territory at +the commencement of the period of occupation; +the male migrant remains there continuously +from the moment it arrives. The male resident +deserts its territory at intervals, even in the +morning; the male migrant betrays no inclination +to do so. Thus there is a very close +correspondence between the behaviour of the +two, and what difference there is—slight after +all—cannot be said to affect the main biological +end of securing territory. One is apt to think +of the problem of migration in terms of the +species instead of in terms of the individual. +One pictures a vast army of birds travelling +each spring over many miles of sea and land, +and finally establishing themselves in different +quarters of the globe; and so it comes about, +I suppose, that a country or some well-defined +but extensive area is regarded as the destination, +the ultimate goal, of the wanderers. But the +resident male has a journey to perform, short +though it may be; it, too, has a destination +to reach, neither a country nor a locality, but +a place wherein the rearing of offspring can<span class='pagenum'><a name="Page_35" id="Page_35">35</a></span> +be safely accomplished, and it, too, arrives in +that place in advance of the female.</p> + +<p>With these facts at our disposal, we will +endeavour to find an explanation. It is unlikely +that specialised behaviour would occur in generation +after generation under such widely divergent +conditions, and, moreover, expose the birds to +risk of special dangers, if it were but an +hereditary peculiarity to which no meaning +could be attached. Hence the appearance of +the males in their breeding haunts ahead of the +females becomes a fact of some importance, and +suggests that the extensive journey in the one +case, and the short journey in the other, may +both have a similar biological end to serve.</p> + +<p>Darwin evidently attached importance to +this difference between the males and the +females in their times of arrival. In the +<i>Descent of Man</i> he referred to it as follows: +"Those males which annually first migrated in +any country, or which in spring were first ready +to breed, or were the most eager, would leave +the largest number of offspring; and these +would tend to inherit similar instincts and +constitutions. It must be borne in mind that +it would have been impossible to change very +materially the time of sexual maturity in the +females without at the same time interfering +with the period of the production of the young—a +period which must be determined by the +season of the year." Newton suggested the +following explanation<a name="FNanchor_2_2" id="FNanchor_2_2"></a><a href="#Footnote_2_2" class="fnanchor">2</a>: "It is not difficult to +<span class='pagenum'><a name="Page_36" id="Page_36">36</a></span> +imagine that, in the course of a journey prolonged +through some 50° or 60° of latitude, +the stronger individuals should outstrip the +weaker by a very perceptible distance, and it +can hardly be doubted that in most species +the males are stouter, as they are bigger +than the females." Granting that the males +are the stronger, how can this account for their +outstripping the females by a week, ten days, +or even a fortnight, in a journey of perhaps +1500 miles? To expect the birds to accomplish +such a distance in seven days is surely +not estimating their capabilities too highly, +and any slight inequality in the power of +flight or endurance could give the males an +advantage of a few hours only. But this explanation, +based upon inequalities in the power +of flight and endurance on the one hand, and +the magnitude of the distance traversed on the +other, cannot afford a solution of the behaviour +of the resident males, and is less likely, therefore, +to be a true solution of that of the +migrants.</p> + +<p>There is another theory, simple enough in its +way, which will probably occur to many. It is +based on the assumption that the males reach +sexual maturity before the females; and it is +contended that the functioning of the instincts +which contribute towards the biological end of +reproduction depend upon the organic changes +which the term "sexual maturity" is held to +embrace, and that, inasmuch as the migratory +instinct belongs to the group of such instincts,<span class='pagenum'><a name="Page_37" id="Page_37">37</a></span> +the males must be the first to leave their winter +quarters.</p> + +<p>What is meant by the "migratory instinct"? +To speak of it as one of the instincts concerned +in reproduction is not enough. Reproduction +involves the actual discharge of the sexual +function, which involves the females; but the +first visible manifestation of organic change in +the male is its desertion of the females. Yet +this is the behaviour which is referred to as the +"migratory instinct," and which comes into play, +according to this theory, because the bird has +reached sexual maturity. Manifestly we must +have some clear understanding as to what these +terms represent. That organic changes determine +the functioning of certain definite instincts +at certain specified times there can be no doubt; +that these changes may occur at a somewhat +earlier date in the male than in the female is +more than probable, but that this explains the +behaviour in question I do not believe. One +wants to know why the changes should occur +earlier in the male, what disposition it is which +first comes into functional activity, and to what +such disposition is related.</p> + +<p>It may, however, be urged that, after all, +this apparent eagerness to reach the breeding +grounds is but a modification of hereditary procedure +under the guiding hand of experience. +What more likely result would follow from the +enjoyment associated with previous success in +the attainment of reproduction than a craving to +repeat the experience? What stronger incentive<span class='pagenum'><a name="Page_38" id="Page_38">38</a></span> +to a hurried return could be imagined? It must +be admitted that there are certain facts which +might be used in support of an appeal to +experience as a reasonable explanation. For +example, the first males to arrive often display +that richness of colouring which is generally +supposed to indicate a fuller maturity. Gätke +even speaks of the "most handsome old birds +being invariably the first to hasten back to their +old homes." But if experience is a factor, if +some dim recollection of the past is held to +explain the hurried departure of the male +migrant, one wants to know with what such +recollection is associated. Is it associated with +the former female, or with the former breeding +place, or with both? I take it that any recollection, +no matter how vague, must be primarily +associated with the particular place wherein +reproduction had previously been accomplished; +and I grant that if the first individuals to +appear were invariably the older and experienced +birds, their early return might be explained on +the basis of such an association. But if there +is reason to believe that a proportion are young +birds on the verge of carrying out their instinctive +routine for the first time, then we cannot +appeal to past experience in explanation of their +behaviour.</p> + +<p>The age of a bird is difficult to determine. +Experience leads me to believe that some of +the males that arrive before the females are +birds born the previous season; one finds, for +instance, individuals with plumage of a duller hue,<span class='pagenum'><a name="Page_39" id="Page_39">39</a></span> +which denotes immaturity, amongst the first +batch of arrivals. But though plumage may +sometimes be a satisfactory guide, yet to rely +upon it alone, or upon a more perfect development +of feather, is to exceed the limits of +safety. How, then, can we ascertain whether +all the males that arrive before the females have +had some previous experience of reproduction? +Well, we take a particular locality and note the +migrants that visit it year after year, and we +find that the respective numbers of the different +species are subject to wide annual fluctuations. +Not every species lends itself to an inquiry of +this kind: some are always plentiful and fluctuation +is consequently difficult to discern; others +are scarce and variation is easily determined. +Those which are of local distribution but conspicuous +by their plumage, or easily traced by +the beauty or the peculiarity of their song, +afford the more suitable subjects for investigation. +For example, the Grasshopper-Warbler, +Marsh-Warbler, Nightingale, Corncrake, Red-backed +Shrike, or Whinchat have each some +distinctive peculiarity which makes them conspicuous, +and each one is subject to marked +fluctuation in numbers. The small plantation or +wooded bank may hold a Nightingale one year, +but we miss its song there the next; the +osier bed or gorse-covered common which vibrates +with the trill of the Grasshopper-Warbler one +April is deserted the following season; the +plantation which is occupied by a host of +common migrants this summer may be enlivened<span class='pagenum'><a name="Page_40" id="Page_40">40</a></span> +next year by the song of the rarer Marsh-Warbler +also; and so on. The fluctuation is +considerable: we observe desertion on the one +hand, appropriation on the other, and yet males +appear before females whether the particular +plantation, osier bed, or swamp had been inhabited +or not the previous season. This fact is +not without significance. It shows that similar +conditions prevail both amongst the males that +appropriate breeding grounds new to them, and +amongst those that return to some well-established +haunt; and on the assumption that +the earlier arrivals are experienced males, the +same birds evidently do not return to the same +place year after year. Granting, then, that the +males which appropriate new breeding-grounds +are young birds, how can their earlier arrival +be explained in terms of past experience; and +granting that they are old, and therefore +experienced, how can it be explained in terms of +association?</p> + +<p>Again, it may be urged that if there is some +biological end to be furthered by this hurried +return, and if recollection of past experience is a +means towards that end, such recollection need +not necessarily be associated with a definite +place, but only in a vague way with the whole +series of events leading up to reproduction—in +which series the migratory journey may even +have acquired meaning. Whether there be any +recollection of a previous journey or of a nest +with young, I do not know. But the young +bird is capable of performing its journey, of<span class='pagenum'><a name="Page_41" id="Page_41">41</a></span> +building its nest, and of rearing its young antecedent +to experience—racial preparation has +fitted it thus far; why then exclude the other +event in the series, the earlier departure of the +male, from hereditary equipment? If the +journey were a casual affair without any goal +attaching to it, if the males upon arrival +wandered about in search of a mate, there would +be some ground for thinking that a vague +recollection of the whole former experience was +sufficient to explain the hurried return; but +since the pleasurable effect of association, +founded upon previous experience of a definite +place, cannot well be established, and since it is +so difficult to study the objective aspect of the +behaviour in question without coming to the +conclusion that the journey is related to the +appropriation of a place suitable for the rearing +of offspring, one is tempted to ask whether the +hurried return may not also be so related.</p> + +<p>Now the males of some of the migratory +species, especially of those which are accustomed +to return to their breeding haunts early +in the season, are called upon to face greater +dangers and have a greater strain imposed +upon their strength by starting forth upon their +journey ten days or a fortnight before their +prospective mates. The blizzards which so often +sweep across the northern parts of Europe in +the latter half of March, destroying in their +course the all too scanty supply of insect life, +may take toll of their numbers; or the westerly +gales, which are not infrequent at that period,<span class='pagenum'><a name="Page_42" id="Page_42">42</a></span> +may meet them in mid-ocean and add to the +perils of their journey; or the temperature of +the previous weeks may have been sufficiently +low to arrest the development of insect life—and +yet males are annually exposed to these +risks in hurrying to their breeding grounds. +For what purpose? The answer will largely +depend upon the way in which we regard those +few acres wherein a resting place is ultimately +found. For myself, I believe that they are +of importance, inasmuch as the securing of a +place suitable for the rearing of offspring is +a primary condition of success in the attainment +of reproduction; and if this be so, it is +evident that the interests of the race will be +better served by the males making good this +first step before the females are ready to pair, +otherwise they might oscillate between two +modes of behaviour, created by the premature +functioning of conflicting impulses.</p> + +<p>The different steps in the process seem to +follow one another in ordered sequence. The +male inherits a disposition—which for us, of +course, has prospective meaning—to seek the +appropriate breeding ground and there to +establish itself; and as early a functioning of +this disposition as possible, consonant with the +conditions of existence in the external environment, +may have been evolved for the following +reasons—firstly, the earlier individuals will +meet with less interference wherever they may +settle, every locality will be open to them, +every acre free, their only need being that<span class='pagenum'><a name="Page_43" id="Page_43">43</a></span> +particular environment for which racial preparation +has fitted them. In the second place, +being already established when other males +appear upon the scene, and advertising their +presence by song, they will be less liable to +molestation; thirdly, in those cases in which +a long journey is undertaken, they will have +ample time to recover from the fatigue, and, +if attacked by later arrivals, will thus be in a +better position to defend their territories; and +lastly, a greater uniformity in their distribution +will be insured before the females begin their +search.</p> + +<p>There is, besides, another good reason for +thinking that the earlier males will have an +advantage. We will assume—and from the +abundant evidence supplied by the marking +of birds, it is quite a reasonable assumption—that +there is a tendency, generally speaking, +for individuals to return to the neighbourhood +of their birthplace, or to the place in which +they had previously reared their offspring. +Now the earlier arrivals will have no difficulty +in securing territories; those that come later +may have to search more diligently, still they +will gain all that they require so long as any +available space remains. Then comes the point +when all suitable ground is occupied, and yet +there are males to be provided for. What +will be the position of these males? Urged by +their inherited nature, they will leave the district +and possibly continue their search into those +adjoining, only, however, to add to the diffi<span class='pagenum'><a name="Page_44" id="Page_44">44</a></span>culties +of the males there similarly situated; +and even allowing that they are at length +successful in establishing themselves, what +are their prospects of securing mates? Since +the earlier females will not extend their wanderings +farther than is absolutely necessary, but +will pair whenever the opportunity for doing +so arises, it is to the later females, forced +onwards by competition, that the late males +must look for mates; so that when at length +pairing does take place, much valuable time +will have been lost.</p> + +<p class="tb">The disadvantages which the late arrivals +have to face are therefore great, and it is +probable that the percentage which attain to +reproduction will on the average be somewhat +lower than the percentage in the case of the +earlier arrivals. The district in which my +observations have been made lies well within +the limits of the breeding range of most of +our common species, and it is not surprising +that I should have met with little evidence +of failure to breed as a result of failure to +secure territory. Some interesting information +was supplied to me, however, by the late +Robert Service. He found, in certain seasons +in Dumfriesshire, flocks of from ten to fifty +unmated Sedge-Warblers, which, from the time +of their arrival in May until the middle of +July, haunted reed-filled spaces along stagnant +streams. These flocks appeared to him to be +composed of loosely-attached individuals of +a migrant flock that had failed to find things<span class='pagenum'><a name="Page_45" id="Page_45">45</a></span> +congenial enough to entice them to disperse. +But may they not have been composed of +males that had failed to secure territories, or +of females that had failed to discover males in +possession of territories, or of both?</p> + +<p>We have seen that, in the case of many +species, each male establishes itself in a +particular place at the commencement of the +breeding season, even though this may mean a +partial or perhaps a complete severance from +former companions. We must now discuss +this fact in greater detail because it is opposed +to the views often held regarding the sexual +behaviour of birds, and is manifestly of importance +when considering the theory of breeding +territory.</p> + +<p>First, however, there is a point which +requires some explanation. I speak of the <i>same</i> +male being in the <i>same</i> place. How can I prove +its identity? In the first place it is highly +improbable that a bird which roams about +within the same small area of ground, makes +regular use of a certain tree and a certain +branch of that tree, and observes a similar +routine day after day, can be other than the +same individual. But, apart from this general +consideration, are there any means by which +individuals of the same species can be identified? +Well, there is variation in the plumage. +Supposing we take a dozen cock Chaffinches +and examine them carefully, we shall find slight +differences in pattern and in colour—more grey<span class='pagenum'><a name="Page_46" id="Page_46">46</a></span> +here or a duller red there, as the case may be—and +though these differences may not be +sufficient to enable us to pick out a bird at +a distance, they are nevertheless conspicuous +when it is close at hand. Then again there is +variation in the song; and the more highly +developed the vocal powers the greater scope +there is for variation. But even the phrases of +a simple song can be split up and recombined +in different ways. If one were asked casually +whether the different phrases of the Reed-Bunting's +song always followed one another in +the same sequence, the answer would probably +be that they certainly did so, whereas the bird is +capable of combining the few notes it possesses +in a surprising number of different ways. And +lastly, there are differences in just the particular +way in which specific behaviour, founded upon +a congenital basis, is adapted by each individual +to its own special environment. Racial preparation +determines behaviour as a whole, but +the individual is allowed some latitude in the +execution of details which are in themselves of +small moment—the selection of a particular tree +as a headquarters and a particular branch upon +that tree, the direction of the distant excursion, +and the direction of the limited wanderings +within the small area surrounding the headquarters +which in the course of time determine +the extent of the territory, are matters for +each individual to decide when the occasion +for doing so arises. Moreover instances of +abnormal coloration or abnormal song are not<span class='pagenum'><a name="Page_47" id="Page_47">47</a></span> +rare, and they are valuable since they place +the identity of the individual beyond dispute. +I can recall the case of a Willow-Warbler whose +song was unlike that of its own or any other +species, and of a Redbreast whose voice puzzled +me not a little. I can recollect also a male Yellow +Bunting whose foot was injured or deformed. +Of this bird's behaviour I kept a record for two +months or so; and inasmuch as it inhabited a +roadside hedge, and was of fearless disposition, +the deformed foot could plainly be seen whenever +it settled upon the road to search for food. +Identification is not, therefore, a difficulty. +There is always some small difference in colour +or in song, or some well-defined routine which +makes recognition possible.</p> + +<p>Owing to their great powers of locomotion, +birds have generally been regarded as wanderers +more or less; anything in the nature of a fixed +abode, apart from the actual nest, having been +accounted foreign to their mode of life; and +even the locality immediately surrounding the +nest has not been apprehended as possessing any +meaning for the owner of that nest. No doubt +the supply of food determines their movements +for a considerable part of the year; they seek +it where they can find it, here to-day, there +to-morrow—in fact few species fail to move +their quarters at one season or another, so that +there is much truth in the notion that birds +are wanderers. Yet to suppose that every +individual one sees or hears—every Lapwing +on the meadow, or Nightingale in the withy<span class='pagenum'><a name="Page_48" id="Page_48">48</a></span> +bed—is in that particular spot just because it +happens to alight there as it roams from place to +place, is to take a view which the observed facts +do not support. For as soon as the question +of reproduction dominates the situation, a new +condition arises, and the habits formed during +the previous months are reversed, and the males, +avoiding one another, or even becoming actively +hostile, prefer a life of seclusion to their former +gregariousness—all of which occurs just at the +moment when we might reasonably expect them +to exhibit an increased liveliness and restlessness +as a result of their endeavour to secure mates; +and so universal is the change that it might +almost be described as an accompaniment of the +sexual life of birds generally.</p> + +<p>That the Raven and certain birds of prey +exert an influence over the particular area which +they inhabit has long been known, and it has +been recognised more especially in the case of +the Peregrine Falcon, possibly because the bird +lives in a wild and attractive country, and, +forcing itself under the notice of naturalists, has +thus had a larger share of attention devoted to its +habits. Moreover, when a species is represented +by comparatively few individuals, and each pair +occupies a comparatively large tract of country, +it is a simple matter to trace the movements +and analyse the behaviour of the birds. There +is a rocky headland in the north-west of +Co. Donegal comprising some seven miles or +so of cliffs, where three pairs of Falcons and two +pairs of Ravens have nested for many years.<span class='pagenum'><a name="Page_49" id="Page_49">49</a></span> +Each year the different pairs have been more +or less successful in rearing their young; each +year the young can be seen accompanying their +parents up to the time when the sexual instinct +arises; and yet the actual number of pairs is on +the whole remarkably constant, and there is no +perceptible increase. It seems as if the numbers +of three and two respectively were the maximum +the headland could maintain. But this +is no exceptional case; it represents fairly the +conditions which obtain as a rule amongst +those species, granting, of course, a certain +amount of variation in the size of each territory +determined by the exigencies of diverse +circumstances.</p> + +<p>If we take a given district, and devote our +attention to the smaller migrants that visit +Western Europe each returning spring for the +purpose of procreation, we shall find that the +movements of the males are subject to a very +definite routine. This, however, is not true of +every male; some may be wending their way to +breeding grounds at a distance; others may be +seeking the particular environment to which +they may be adapted; others again, having found +their old haunts destroyed, may consequently +be seeking new.</p> + +<p>Of all this there is evidence. Small parties +of Chiffchaffs pass through a district on their +way to other breeding grounds, flitting from +hedge to hedge as they move in a definite +direction with apparently a definite purpose; +Reed-Warblers settle in a garden or plantation,<span class='pagenum'><a name="Page_50" id="Page_50">50</a></span> +eminently unsuited to their requirements, and +disappear; Wood-Warblers arrive in some old +haunt, and finding it no longer suitable for +their purpose, seek new ground. So that plenty +of individuals are always to be found, which, for +the time being at least, are wanderers.</p> + +<p>In the district which I have in mind, the +wandering males form only a small part of the +incoming bird population. The majority of +individuals that fall under observation are those +that have made this particular district their +destination; and in doing so, they may possibly +have been guided by their experience as owners +or inmates of former nests, for it cannot be +doubted that a return to the neighbourhood of +the birthplace would lead to a more uniform +distribution and therefore be advantageous, and +the tendency to do so might consequently have +become interwoven in the tissue of the race. +How, then, do they behave? A certain amount +of movement, an interchanging of positions, even +though restricted to an area defined, let us say, +by experience, might be expected under the +circumstances—that, however, is not what we +find; we observe the available situations plotted +out into so many territories, each one of which +is occupied by a male who passes the whole of +his time therein. Take whatever species we +will—Whitethroat, Whinchat, Willow-Warbler, +Red-backed Shrike, it matters not which, for +there is no essential difference in the general +course of procedure—this condition will be +found to prevail. Generally speaking, the<span class='pagenum'><a name="Page_51" id="Page_51">51</a></span> +behaviour in relation to the territory can be +studied more conveniently where a number of +individuals of the same species have established +themselves in proximity to one another. Such +species as the Chiffchaff, Willow-Warbler, or +Wood-Warbler are often sufficiently common to +allow of three or more of their respective males +being kept in view at the same time; and the +disposition to occupy a definite position can be +readily observed. The Reed-Warbler is a suitable +subject for an investigation of this kind; +for since it is restricted by its habits to localities +wherein the common reed (<i>Arundo phragmites</i>) +grows in abundance, and since such localities +are none too plentiful and often limited in +extent, the area occupied by each individual is +necessarily small—if it were not so the species +would become extinct. Hence it is a simple +matter to study the routine of the different +individuals and to mark the extent of their +wanderings.</p> + +<p>In this way the males of all the Warblers +that breed commonly in Great Britain establish +themselves, each one in its respective station at +the respective breeding ground; so, too, do +those of many other migrants—for example, the +Whinchat, Wheatear, Tree-Pipit, and Red-backed +Shrike. All of these, it is true, are +common species—numbers of individuals can +often be found in close proximity—and therefore +it may be argued that they keep to one position +more from pressure of population than from any +inherited disposition working towards that end.<span class='pagenum'><a name="Page_52" id="Page_52">52</a></span> +But the rarer species behave similarly. Districts +frequented by the Marsh-Warbler and offering +plenty of situations of the type required by the +bird are often inhabited by a few members only, +and yet the disposition to remain in a definite +position is just as marked.</p> + +<p>You will say, however, that these smaller +migrants have no exceptional powers of flight; +that they have besides just completed a long +and arduous journey; and you will ask why +they should be expected to wander, whether it +is not more reasonable to expect that, in order +to overcome their fatigue, they should remain +where they settle. The Cuckoo is a wanderer +in the wider sense of the term, and is gifted with +considerable powers of flight. Upon arrival the +male flies briskly from field to field, showing but +little signs of weariness; yet we have only to +follow its movements for a few days in succession +to assure ourselves that the bird is no longer +a wanderer; for just as the Warbler or the Chat +moves only within a definitely delimited area, +so the male Cuckoo, strange as it may seem, +restricts itself to a particular tract of land. +The area over which it wanders is often considerable +and consequently it is not possible to +keep the bird always in view, but inasmuch +as the variation in the voices of different +individuals is quite appreciable, identification is +really a simple matter. If we cannot keep the +bird in sight, we can trace its movements by +sound and mark the extent of its wanderings, +which by repetition become more and more<span class='pagenum'><a name="Page_53" id="Page_53">53</a></span> +defined, until a belt of trees here, or an orchard +there, mark a rough and rarely passed boundary +line.</p> + +<p>Let us take another example from the larger +migrants—the Black-tailed Godwit, a bird +common enough in the Dutch marshes but no +longer breeding in this country. On suitable +stretches of marsh land, numbers will be found +in proximity one to another after the manner +of the Lapwing, each male occupying a definite +space of ground wherein it passes the time +preening, searching for food, or in sleep—though +at the same time keeping a strict watch +over its territory. Now the preference shown +for a particular piece of ground, and the determination +with which it is resorted to, is the +more remarkable when we take into consideration +the specific emotional behaviour arising +from the seasonal sexual condition. This +behaviour is expressed in a peculiar flight. The +bird rises high in the air, circles round with +slowly beating wings above the marsh, and +utters a call which, as far as my experience goes, +is characteristic of the performance. The air +is often full of individuals circling thus even +beyond the confines of the marsh, for a male +does not limit its flight to a space immediately +above its territory; but nevertheless careful +observation will show how unerringly each one +returns to its own position on the breeding +ground, no matter how extensive the aerial +excursion may have been. And so, when the +males of the smaller migrants confine their<span class='pagenum'><a name="Page_54" id="Page_54">54</a></span> +movements to an acre of ground at the completion +of their long journey, they are acting no +more under the influence of fatigue than the +Cuckoo, which keeps within certain bounds yet +flies about briskly, or the Godwit which, though +holding to its few square yards on the ground, +executes most tiring and extensive flights above +the marsh.</p> + +<p>Of all the migrants, however, the behaviour +of the Ruff is perhaps the most strange, and +though it has long been known that these birds +have their special meeting places where they +perform antics and engage in serious strife, yet +it is only within recent years that the primary +purpose of these gatherings has been ascertained—that +purpose being the actual discharge of +the sexual function. Mr. Edmund Selous has +carried out some exhaustive investigations into +their activities at the meeting places, and he +makes it clear that each bird has its allotted +position. He says, for example, that "It begins +to look as though different birds had little +seraglios of their own in different parts of the +ground," that "each Ruff has certainly a place +of its own," or again that "this Ruff indeed, +which I think must be a tender-foot, does not +seem to have a place of its own like the others." +Nevertheless it is only at the meeting places +that they have their special positions; there is +no evidence to show that each one has a special +territory, wherein it seeks its food, as the +Warbler has, and therefore some may think that +we are here confronted with behaviour of a<span class='pagenum'><a name="Page_55" id="Page_55">55</a></span> +different order. But we must bear in mind that +the process has been adjusted to meet the +requirements of different species: the size of the +territory, the period of its daily occupation, the +purpose which it serves—these all depend upon +manifold relationships and do not affect the +principle. Why it has been differentiated in +different circumstances we shall have occasion +to discuss later; for the moment it is enough +that at the end of its migratory journey each +Ruff occupies one position on the meeting +ground.</p> + +<div class="figcenter" style="width: 500px;"><a name="f073" id="f073"></a><img src="images/fig073.jpg" width="500" height="404" +alt="Territorial flight of the Black-tailed Godwit." title="Territorial flight of the Black-tailed Godwit." /></div> + +<p>Now birds that are paired for life, whose +food-supply is not affected by alternations of +climate, have no occasion to desert the locality +wherein they have reared their offspring, and so +their movements, being subject to a routine +which would tend to become increasingly +definite, must in the course of time and according +to the law of habit formation become +organised into the behaviour we observe. Is it +necessary, therefore, to seek an explanation of +their tendency to remain in one place in anything +so complex as an inherited disposition? +Again, since we have to confess to so very much +ignorance on so many points connected with the +whole phenomenon of migration, may there not +be some condition, hitherto shrouded in mystery, +which might place so different a complexion on +the corresponding aspect of migrant behaviour +as to rid us, in their case also, of the necessity +of appealing to an inherited disposition? Such +questions are justifiable. And if the life-histories<span class='pagenum'><a name="Page_56" id="Page_56">56</a></span> +of other species gave no further support +to our interpretation, if, in short, the evidence +were to break down at this point, then we +should be forced to seek some other explanation +more in keeping with the general body of +facts.</p> + +<p>But far from placing any obstacle in the way +of an interpretation in terms of inherited disposition, +the behaviour of many of those residents +which are not paired for life gives us even surer +ground for that belief. Moreover in their case +the initial stages in the process are more accessible +to observation. I will endeavour to explain +why. In the process of reproduction the +environment has its part to play—whether in the +manner here suggested, or indirectly through +the question of food-supply, matters not at the +moment. Now, migratory species are more +highly specialised than resident species as +regards food, and are affected more by variations +of temperature, so that they can live for only a +part of the year in the countries which they visit +for the purpose of procreation. Hence the +organic changes, which set the whole process in +motion, must be coincident in time with the +growth of appropriate conditions in the environment; +for if it were not so, if the internal +organic changes were to develop prematurely, +the bird would undertake its journey only to +find an insufficiency of food upon its arrival, and +this would scarcely contribute towards survival. +Definite limitations have therefore been imposed +upon the period of organic change. But in the<span class='pagenum'><a name="Page_57" id="Page_57">57</a></span> +case of many resident species the conditions are +somewhat different, for they remain in the same +locality throughout the year, and a gradual +unfolding of the reproductive process cannot +therefore have a similarly harmful effect. Thus +it comes about that the behaviour of the +migrant, when it arrives at the breeding ground +and first falls under observation, represents a +stage in the process which, in the case of the +resident, is only reached by slow degrees; and +by closely observing the behaviour as it is +presented to us in the life of the resident male, +we not only gain a better insight into the +changes in operation, but can actually witness +the breaking down of the winter routine, stereotyped +through repetition, by the new disposition +as it arises.</p> + +<p>The first visible manifestations, even though +they may be characterised by a certain amount +of vagueness, are therefore of great importance +if the behaviour is to be interpreted aright; and +in order to insure that none of these earlier +symptoms shall be missed, it is necessary to +begin the daily record of the bird's movements +at an early date in the season. As a rule the +second week in February is sufficiently early for +the purpose, but the date varies according to the +prevailing climatic conditions. Even in species +widely remote there is great similarity of procedure, +and the behaviour of the Buntings is +typical of that of many. With the rise of the +appropriate organic state the male resorts at +daybreak to a suitable environment, occupies a<span class='pagenum'><a name="Page_58" id="Page_58">58</a></span> +definite position, and singling out some tree or +prominent bush, which will serve as a headquarters, +advertises its presence there by song. +At first the bird restricts its visits, which though +frequent in occurrence are of short duration, for +the most part to the early hours of the morning; +it disappears as suddenly as it appeared, and +one can trace its flight to the feeding grounds—a +homestead or perhaps some newly sown +field. But by degrees the impulse to seek the +society of the flock grows less and less pronounced, +the visits to the territory are more +and more prolonged, and the occupation of +it then becomes the outstanding feature of +the bird's existence. This in outline is the +course of procedure as it appears to an external +observer.</p> + +<p>But although much can be learnt from the +lives of these smaller species, there is no gain-saying +the fact that a great deal of patient +observation is required, and the process is apt +to become tedious. There are others, however, +which are more readily observed, whilst their +life-histories afford just as clear an insight into +the effect produced by the new disposition +upon the developing situation; and among these +the Lapwing takes a prominent position, because +it is plentiful and inhabits open ground where +it is easily kept in view.</p> + +<div class="figcenter2" style="width: 500px;"><a name="f080" id="f080"></a><a href="images/fig080z.jpg"><img src="images/fig080.jpg" width="500" height="342" alt="Plan of the +water meadow showing the territories occupied by Lapwings in the year +1915." title="Plan of the water meadow showing the territories occupied +by Lapwings in the year 1915." /></a></div> + +<p class="caption">Plans of the Water-meadow showing the Territories occupied by Lapwings in 1915.</p> + +<div class="figcenter2" style="width: 500px;"><a name="f081" id="f081"></a><a href="images/fig081z.jpg"><img src="images/fig081.jpg" width="500" height="333" alt="Plan of the +water meadow showing the territories occupied by Lapwings in the year +1915." title="Plan of the water meadow showing the territories occupied +by Lapwings in the year 1915." /></a></div> + +<p class="caption">Plans of the Water-meadow showing the Territories occupied by Lapwings in 1916</p> + +<p>There is a water meadow with which I am +familiar, where large numbers resort annually +for the purpose of procreation. Here they +begin to arrive towards the end of February,<span class='pagenum'><a name="Page_59" id="Page_59">59</a></span> +and at first collect in a small flock at one end +of the meadow. A male, here and there, can +then be seen to break away from the flock, and +to establish itself in a definite position upon the +unoccupied portion of the ground, where it +remains isolated from its companions. Others +do likewise until the greater part of the meadow +is divided into territories. Six of these territories +I kept under observation for approximately +two months in the year 1915. The occupant +of the one marked No. 6 upon the 1915 plan +was a lame bird, a fortunate occurrence as it +enabled me to follow its movements with some +accuracy; and though it maintained its position +for some weeks, it ultimately disappeared, as a +result, I believe, of the persistent attacks of +neighbouring males. The behaviour of the +males during the first fortnight or so after +they broke away from the flock was interesting. +Though they retired to their territories and +remained in them for the greater part of their +time, yet it was only by degrees that they +finally severed their connection with the flock, +for so long as a nucleus of a flock remained, +so long were they liable to desert their +territories temporarily and to rejoin their +companions.</p> + +<p>Lapwings, as is well known, collect in flocks +during the winter months, and these flocks, +which sometimes reach vast proportions, are +to be found on tidal estuaries, water meadows, +arable land, and such like places, according to +the prevailing climatic conditions. This flocking<span class='pagenum'><a name="Page_60" id="Page_60">60</a></span> +may contribute towards survival, and may +therefore be the result of congenital dispositions +which have been determined on biological +grounds. On the other hand, since food at +that season is only to be obtained in a limited +number of situations, the birds may be simply +drawn together by accident. In the former +case the behaviour would be instinctive, in +the latter, though accidental at first, recurrent +repetition would tend to make it habitual; but +in either case the impulse to accompany the +flock must be a powerful one, for on the one +hand it would depend upon inherited, and on +the other hand upon acquired, connections in +the nervous system. Now observe that soon +after the flock arrived in the meadow, single +males detached themselves; there was no +hesitation, they just retired from their companions +and settled in their respective territories. +They were not expelled, for if their leaving had +been compulsory much commotion would have +preceded their departure, and their return +would certainly not have been welcomed. A +reference to the plan will make the position +clearer; the neutral zone inhabited by the +flock is there shown as situated in one corner +of the meadow, the territories that fell under +observation are plotted out as far as possible +to scale, and the more important zones of +conflict are also marked.</p> + +<p>The males spent part of their time in their +respective territories and part with the flock, +so long as it remained in existence. When a<span class='pagenum'><a name="Page_61" id="Page_61">61</a></span> +male was in its territory it avoided companions +and was openly hostile to intruders; when it +was with the flock it wandered about with +companions in search of food. The contrast +between the two modes of behaviour was very +marked, and it was evident that the gregarious +instinct was gradually yielding its position of +importance to the new factor—the territory. +If there had been no flock, if a few solitary +individuals had appeared here and there and +had established themselves in different parts of +the meadow, one would have had no definite +evidence of the strength of the impulse in the +male to seek a position of its own, one could +only have argued from the general fact of males +flocking in the winter and isolating themselves +in spring that something more than accident +was required to explain so radical a change. +But since the birds returned in a flock to the +ground upon which they intended to breed, and +since the flock occupied temporarily part of +the ground whilst the partitioning of the +remainder was still proceeding, it was possible +to gauge the strength of the impulse, which was +forcing the males to isolate themselves in +particular areas of ground, by comparing it +with the impulse to accompany the flock—and +the measure of its intensity was the rapidity +with which the latter impulse yielded its position +of importance.</p> + +<p>Like the Lapwing, the Coot and Moor-Hen +are easily kept under observation, and since +many individuals often breed in proximity,<span class='pagenum'><a name="Page_62" id="Page_62">62</a></span> +more than one can be watched at the same +moment; moreover the area occupied by each +male generally embraces an open piece of +water as well as part of the fringe of reeds, +so that the movements of the bird can be +followed without much difficulty. Under favourable +conditions manifestations of the developing +situation become visible at a comparatively +early date in the season—the middle or the +latter part of February—and these manifestations +resemble those of other species. But +the Moor-Hen passes summer and winter alike +in the same situation, and being therefore in +a position to respond at once to internal stimulation, +however vague, the change from the one +state to the other is gradual. This, however, +is a matter of detail; the main consideration +lies in the fact that the impulse to retire to +a definite position, to avoid companions, and +to live in seclusion, is strongly marked, and +produces a type of behaviour similar on the +whole to that of the Lapwing. First of all +there is the appropriation of a certain position, +the limits of which are fixed according to the +law of habit formation, and according to the +pressure exerted by neighbouring individuals; +then there is the neutral ground over which +the birds wander amicably in search of food; +and finally there is the contrast between the +pugnacity of the male whilst in its territory, +and its comparative friendliness when upon +neutral ground.</p> + +<p>Evidence of similar behaviour is to be found<span class='pagenum'><a name="Page_63" id="Page_63">63</a></span> +in the life of the Black Grouse, a bird which has +always excited the curiosity of naturalists on +account of the special meeting places to which +both sexes resort in the spring. Mr. Edmund +Selous watched these birds in Scandinavia, +where he kept a daily record at one of the +meeting places. In various passages he refers +to the appropriation of particular positions by +particular males, and concludes thus: "It would +seem from this that, like the Ruffs, each male +Blackcock has its particular domain on the +assembly ground, though the size of this is in +proportion to the much greater space of the +whole. On the other mornings, too, the same +birds, as I now make no doubt they are, +have flown down into approximately the same +areas."</p> + +<p>The cliff-breeding species—Guillemots, Razorbills, +and Puffins—are difficult to investigate +because individuals vary so little, and the sexes +resemble one another so closely; yet, despite +these difficulties, we can gain some idea of the +general purport of their activities. But when +the ledges are crowded and the air is filled with +countless multitudes, how is it possible to keep +a single bird in view for a sufficient length of +time to understand its routine? The difficulty +is not an insuperable one. The flights, undertaken +seemingly for no particular purpose, are +often of short duration and are completed before +the strain of observation becomes too great; +moreover an individual sometimes possesses a +special mark or characteristic which serves to<span class='pagenum'><a name="Page_64" id="Page_64">64</a></span> +make it conspicuous. For example, there is a +well-marked variety of the Common Guillemot, +the Ringed or Bridled Guillemot of science, +distinguished by an unusual development of +white round the eye and along the furrow +behind it. One such individual I was fortunate +in discovering upon a crowded cliff, and, as in +the case of the Lapwing with the broken +leg or the Yellow Bunting with the injured +foot, the identity of the bird was beyond dispute, +and one could observe that it appropriated +to itself a particular position upon a particular +ledge.</p> + +<p>Guillemots and Razorbills return at intervals +to the breeding stations early in the season, and +these visits are repeated with growing frequency +until the birds are finally established. I have +witnessed these periodic returns during March +in the south of England, and during April in +the north-west of Ireland, and I am informed +that in the latter district such visits may occur +as early as February. Gätke, who had ample +opportunity of observing the birds in Heligoland, +puts their return at an even earlier date. "They +visit their breeding places," he says, "in flocks +of thousands at the New Year, often even as +early as December, as though they wanted to +make sure of their former haunts being well +preserved and ready for their reception." Such +visits, however, are irregular in occurrence; the +birds arrive, and, after spending a short time +upon the ledges, disappear. And since there is +not the same evidence in their coming and going<span class='pagenum'><a name="Page_65" id="Page_65">65</a></span> +of that method which we observe in the +periodical returns of the Bunting or the Finch, +it may be thought that needless importance +is being attached to an episode in their lives +which is quite intelligible in terms of a feeble +response determined by a dawning organic +change. While it may be quite intelligible in +such terms it is not thereby explained; for +every response must have as its antecedent an +inherited connection in the nervous system +determined on biological grounds. Besides, +these early periodic returns conform in general +to the type of behaviour displayed by other +species, the males of which return to their breeding +grounds many weeks before the real business +of reproduction begins. Are we then justified in +regarding them as accidents of the developing +situation? Are we not rather bound to admit +that they have some definite biological end to +serve?</p> + +<div class="figcenter" style="width: 500px;"><a name="f089" id="f089"></a><img src="images/fig089.jpg" width="500" height="866" +alt="Competition for territory is seldom more severe than +amongst cliff-breeding sea birds, and the efforts of +individual Razorbills to secure positions on the +crowded ledges lead to desperate struggles.." title="Competition for territory is seldom more severe than +amongst cliff-breeding sea birds, and the efforts of +individual Razorbills to secure positions on the +crowded ledges lead to desperate struggles." /></div> + +<p class="tb">These examples show that the males of many +species reverse their mode of life at the commencement +of the breeding season and proceed +to isolate themselves, each one in a definitely +delimited area.</p> + +<p>There are three ways in which we may +attempt to interpret this particular mode of +male behaviour. We may regard it as an +accidental circumstance, nowise influencing the +course of subsequent procedure; or, appealing +to the law of habit formation, we may +regard it as an individual acquirement; or<span class='pagenum'><a name="Page_66" id="Page_66">66</a></span> +again, we may invest it with a deeper significance +and seek its origin in some specific +congenital disposition determined on purely +biological grounds.</p> + +<p>Which of these three shall we choose? The +first by itself requires but little consideration; +for though it might explain the initial visit, it +cannot account for the persistency with which +the plot of ground is afterwards resorted to. +Supposing, however, that we combine the first +and the second; supposing, that is to say, we +assume, for the purpose of argument, that the +initial visit is fortuitous, and that constancy is +supplied by habit formation—would that be a +satisfactory interpretation? It is a simple one, +inasmuch as it only requires that a male shall +alight by chance in a particular place for a few +mornings in succession in order that the process +may be set in motion. Now an essential condition +of habit formation is recurrent repetition; +given this repetition and, it is true, any mode of +activity is liable to become firmly established. +But how can we explain the repetition? Even +if we are justified in assuming that the initial +visit is purely an accidental occurrence, we +cannot presume too far upon the laws of chance +and assume that the repetition, at first, is also +fortuitous.</p> + +<p>So that we come back to the congenital +basis, the last of our three propositions. And it +will, I think, be admitted that the facts give us +some grounds for believing that the securing of +the territory has its root in the inherited con<span class='pagenum'><a name="Page_67" id="Page_67">67</a></span>stitution +of the bird. In comparing the behaviour +of the migratory male with that of the resident, +attention was drawn to the manner in which +the occupation of a territory was effected: the +former bird, it may be remembered, established +itself without delay, whereas the latter did so +only by degrees, and the difference was attributed +to the incidence of migration which required +a closer correspondence between organic process +and external environment. But the significance +for us just now lies in the fact that the definiteness, +which accompanies the initial behaviour of +the migratory male in relation to the territory, +cannot have been acquired by repetition; for +this reason, that when the male occupies its +space of ground at the end of its long and +arduous journey, it does so without preparation +or experiment, even without hesitation, as if +aware that it was making good the first step in +the process of reproduction. No doubt, if it +happened to be an individual that had already +experienced the enjoyment of reproduction, it +might be aware of the immediate results to be +achieved and act accordingly. But among the +hosts of migrants that one observes, there must +be many males which have not previously mated; +and yet, upon arrival, they all behave in a +similarly definite manner—so that experience +cannot well be the primary factor in the situation. +If, then, the essential condition of habit +formation is absent and experience is eliminated, +there is nothing left but racial preparation to fall +back upon.</p> + +<p><span class='pagenum'><a name="Page_68" id="Page_68">68</a></span>Nevertheless, it is true that many resident +males seem to pass through a period of indecision +before they establish themselves permanently +in their respective territories; they come and +go, their visits grow more and more prolonged, +and only after the lapse of some +considerable time does the process of establishment +attain that degree of completeness which +is represented in the initial behaviour of the +migratory male. Their whole procedure seems +therefore to bear the stamp of individual acquirement; +and, if it stood alone, we might be +content to construe it thus, but the example +of the migratory male necessitates our looking +elsewhere for the real meaning of the +indecision.</p> + +<p>Let me first of all give some instances of the +persistence with which a male remains in one +spot, and this despite the fact that it has +no mate.</p> + +<p>A Reed-Bunting occupied a central territory +in a strip of marshy ground inhabited annually +by four or five males of this species. Throughout +April, May, and until the 19th June, it +clung to its small plot of ground, tolerated no +intrusion, and sang incessantly.</p> + +<p>Two Whitethroats arrived at much the +same time—the 30th April approximately—and +occupied the corner of a small plantation; +the one obtained a mate the day following +its arrival, the other remained unpaired for a +fortnight.</p> + +<p>A Reed-Warbler established itself amongst<span class='pagenum'><a name="Page_69" id="Page_69">69</a></span> +some willows and alders adjoining a reed-bed +and made its headquarters in a small willow +bush. Not more than fifteen yards away, on the +edge of the main portion of the reeds, another +male was established and was paired on the 22nd +May. Each morning the single male behaved +in much the same way, singing continuously +whilst perched upon the bush. And so the +days passed by until it seemed improbable +that it would ever secure a mate, but one +appeared on the 20th June, and a nest was built +forthwith.</p> + +<p>Now it is difficult to believe that a chance +visit, even though repeated for a few mornings +in succession, could have accounted for the +Reed-Bunting remaining so persistently in the +marsh, or the Whitethroat in one corner of the +osier bed, or the Reed-Warbler in that one +particular willow. Not only so, but if a habit of +such evident strength can be acquired so readily, +we have a right to ask why it should only be +acquired in the spring—why not at every season? +Considerations such as these lead to the belief +that there must be some congenital basis to +account for such persistent endeavour; the more +so since it is difficult not to be impressed with +the conative aspect of the male's behaviour. To +a stranger, unacquainted with its previous +history, the bird might appear to be leading a +life of hesitation, whereas, if carefully watched, +its whole attitude will be found to betray +symptoms of a striving towards some end; and +the frequent departure and return, which might<span class='pagenum'><a name="Page_70" id="Page_70">70</a></span> +be pointed to as the material from which a +definite mode of procedure would be likely to +emerge, is in reality behaviour of a determinate +sort.</p> + +<p>My interpretation, then, of the apparent +indecision in the behaviour of the resident male +is this. During the winter most species live in +societies, together they seek their food and +together they retire in the evening to the +accustomed roosting places; and the association +of different individuals confers mutual benefits +upon the associates. The movements of these +societies are dominated by the question of food; +all else is subservient, and the supply of the +necessary sustenance may, under certain conditions, +become a difficulty which can only be +met by energy and resource. After the long +night the sensation of hunger is strong, and the +birds, on awakening, fly to the accustomed +feeding grounds, returning again in the evening +to the selected spot, and by frequent repetition +a routine becomes established. Thus +the behaviour of each individual is determined +not only by the powerful gregarious impulse +but also by the habits formed in connection +therewith during many weeks in succession. +Now with the rise of the appropriate organic +state, the disposition to seek the breeding +ground and there to establish itself becomes +dominant in the male. But the process is a +gradual one. There is no need, as happens +amongst the migrants, for the period of organic +change to conform rigidly to the growth of<span class='pagenum'><a name="Page_71" id="Page_71">71</a></span> +any particular condition in the environment, +and hence for a time the bird oscillates between +two modes of behaviour—between that one +organised by frequent repetition and that one +determined by the functioning of this new +disposition.</p> + +<p>To look at the matter broadly, it is scarcely +likely that so definite a mode of behaviour would +recur with such regularity, generation after +generation, in the individuals belonging to so +many widely divergent forms, if it had no root +in the inborn constitution of the bird. But the +law of habit formation has its part to play also. +By itself it is inadequate; yet it probably does +assist very materially in adding still greater +definition, and it probably is responsible in a +large measure for determining the limits of +the territory according to the conditions of +existence of the species—thus the Falcon +seeks its prey over wide tracts of land, and, +by hunting over certain ground repeatedly, +establishes a routine, which broadly fixes the +area occupied; the Woodpecker cannot find +food upon every tree, and every forest does +not contain the necessary trees, and therefore +the bird regulates its flight according to the +position of the trees; and the Warbler, finding +food close at hand, does not need to travel +far, and the area it occupies is consequently +small.</p> + +<p>So that the most likely solution of the +problem will be found in a combination of our +second and third propositions; that is to say, in<span class='pagenum'><a name="Page_72" id="Page_72">72</a></span> +an initial responsive behaviour provided for in +the inherited constitution of the nervous system, +and in a definiteness acquired by repetition and +determined by relationships in the external +environment.</p> +<hr /> +<p><span class='pagenum'><a name="Page_73" id="Page_73">73</a></span></p> +<h3>CHAPTER III</h3> + +<h4>THE DISPOSITION TO DEFEND THE TERRITORY</h4> + + +<p>In the previous chapter I endeavoured to show +that each male establishes a territory at the +commencement of the breeding season, and there +isolates itself from members of its own sex. +And further I gave my reasons for believing +that this particular mode of behaviour is determined +by the inherited nature of the bird, and +that we are justified in speaking of it as "a +disposition to secure a territory" because we can +perceive its prospective value. But the act of +establishment is only one step towards "securing." +By itself it can achieve nothing; for any number +of different individuals might fix upon the same +situation, and if there were nothing in the +inherited constitution of the bird to prevent +this happening, where would be the security, or +how could any benefit accrue to the species?</p> + +<p>In withdrawing from its companions in the +spring, the male is breaking with the past, and +this action marks a definite change in its routine +of existence. But the change does not end in +attempted isolation; it is carried farther and +extends to the innermost life and affects what,<span class='pagenum'><a name="Page_74" id="Page_74">74</a></span> +humanly speaking, we should term its emotional +nature, so that the bird becomes openly hostile +towards other males with whom previously it +had lived on amicable terms.</p> + +<p>The seasonal organic condition is responsible +for the functioning of the disposition which +results in this intolerance, just as it is for +the functioning of the disposition which leads +to the establishment of the territory; and the +effect of these two dispositions is that a space of +ground is not only occupied but made secure +from intrusion. The process is a simple one. +There is no reason to believe, there is no +necessity to believe, that any part of the procedure +is conditioned by anticipatory meaning; +the behaviour is "instinctive" in Professor +Lloyd Morgan's definition of the word, since it +is of a "specific congenital type, dependent upon +purely biological conditions, nowise guided by +conscious experience though affording data for +the life of consciousness."</p> + +<p>That the males of many animals are apt to +become quarrelsome during the mating period is +notorious. Darwin collected a number of facts, +many of which related to birds, showing the +nature and extent of the strife when the sexual +instinct dominated the situation. And pondering +over these facts, he deduced therefrom a "law of +battle," which, he believed, bore a direct relation +to the possession of a female. And it must +be admitted that he had excellent ground for his +conclusion in the fact not only that the conflicts +occur mainly during the pairing season, but that +<span class='pagenum'><a name="Page_75" id="Page_75">75</a></span> +the female is often a spectator and seems even to +pair with the victor. I accepted it, therefore, as +the most reasonable interpretation of the facts. +But, as time passed by, incidents of a conflicting +character led me to think that after all there +might be another solution of the problem. And +when it was no longer possible to doubt that +there was a widespread tendency to establish +territories, it at once became manifest that the +battles might have an important part to play in +the whole scheme. But how was this to be +proved? What sort of evidence could show +whether the proximate end for which the males +were fighting had reference to the female or to +the territory? Clearly nothing but a complete +record of the whole series of events leading up +to reproduction could supply the necessary data +upon which a decision might rest. In the +present chapter I shall give, in the first place, +the reasons which lead me to think that the +origin of the fighting cannot be traced to the +female; afterwards, the evidence which seems to +show that it must be sought in the territory; +and finally, I shall make a suggestion as to the +part the female may play in the whole scheme.</p> + +<div class="figcenter" style="width: 500px;"><a name="f101" id="f101"></a><img src="images/fig101.jpg" width="500" height="426" +alt="Male Blackbirds fighting for the possession of territory. +The bare skin on the crown of the defeated bird shows the +nature of the injuries from which it succumbed." title="Male Blackbirds fighting for the possession of territory. +The bare skin on the crown of the defeated bird shows the +nature of the injuries from which it succumbed." /></div> + +<p>The facts upon which the "law of battle" +was founded were ample to establish the truth of +its main doctrine. But the evidence upon which +the interpretation of the battles was based was +somewhat superficial. It was based mainly upon +the general observation that one or more females +could frequently be observed to accompany the +combatants; and if this were the sole condition<span class='pagenum'><a name="Page_76" id="Page_76">76</a></span> +under which the fighting occurred, one must +admit that this view would have much to +recommend it. But it is not merely a question +of males disputing in the presence of a female; +for males fight when no female is present, pair +attacks pair, or a male may even attack a female—in +fact there is a complexity of strife which is +bewildering.</p> + +<p>In attributing the rivalry to the presence +of the female, it is assumed that males are in +a preponderance, and that consequently two or +more are always ready to compete for a mate. +Her presence is presumably the condition under +which his pugnacious nature is rendered susceptible +to its appropriate stimulus, the stimulus +being, of course, supplied by the opponent. +There would be nothing against this interpretation +if it were in accord with the facts; but it +can, I think, be shown that the males are just +as pugnacious and the conflicts just as severe +even when the question of securing a mate +is definitely excluded; and I shall now give the +evidence which has led me to this conclusion.</p> + +<p>In the previous chapter we had occasion to +refer to the difference in the times of arrival +of the male and female migrants, and we +came to the conclusion, it may be remembered, +that this was a fact of some importance, +because it gave us a clue to the meaning +of much that was otherwise obscure in their +behaviour. But it is also of importance in +connection with the particular aspect of the +problem which we now have in view, for if it<span class='pagenum'><a name="Page_77" id="Page_77">77</a></span> +can be shown that males, when they first reach +their breeding grounds, are even then intolerant +of one another's presence, if their actions and +attitudes betray similar symptoms of quasi-conation, +if disputes are rife and the struggles +of a kind to preclude all doubt as to their +reality, then it is manifest that in such cases +their intolerance cannot be due to the presence +of the female.</p> + +<p>Here, however, I must refer to a view which +is held by some psychologists, namely, that +amongst the higher animals, even on the +occasion of the first performance of an instinctive +act, there is some vague awareness of the +proximate end to be attained. Discussing the +nature of instincts, Dr M'Dougall<a name="FNanchor_3_3" id="FNanchor_3_3"></a><a href="#Footnote_3_3" class="fnanchor">3</a> says, "Nor +does our definition insist, as some do, that the +instinctive action is performed without awareness +of the end towards which it tends, for this, +too, is not essential; it may be, and in the case +of the lower animals no doubt often is, so +performed, as also by the very young child, +but in the case of the higher animals some +prevision of the immediate end, however vague, +probably accompanies an instinctive action that +has often been repeated." A similar view seems +to be held by Dr Stout.<a name="FNanchor_4_4" id="FNanchor_4_4"></a><a href="#Footnote_4_4" class="fnanchor">4</a> "As I have already +shown," he says, "animals in their instinctive +actions do actually behave from the outset as +if they were continuously interested in the +development of what is for them one and the +same situation or course of events; they actually +<span class='pagenum'><a name="Page_78" id="Page_78">78</a></span>behave as if they were continuously attentive, +looking forward beyond the immediately present +experience in preparation for what is to come. +They apparently watch, wait, search, are on the +alert. They also behave exactly as if they +appreciated a difference between relative success +and failure, trying again when a certain perceptible +result is not attained and varying their +procedure in so far as it has been unsuccessful. +All these characters are found in the first nest-building +of birds as well as in the second; they +are found also in courses of conduct which occur +only once in the lifetime of the animal." Both +these writers would, I imagine, contend that, +even when a female is absent, the idea of the +female, as the end in view throughout, is +present; and they would argue that the fact +of her absence during the fighting in no way +disposes of the belief that she is the condition +under which the pugnacious instinct of the +male is rendered susceptible to stimulation. +What reason is there to think that this interpretation +is applicable to the case under consideration? +When a female is present, we +observe that the males are pugnacious, and, +when she is absent, that they still continue to +be hostile—that is to say, they behave <i>as if</i> she +were present. Now, as far as I can ascertain, +the "<i>as if</i>" is the only ground there is for +supposing that the female is represented in +imaginal form—there is no evidence of the +fact, if fact it be. On the contrary, the behaviour +of the male affords some fairly conclusive evidence<span class='pagenum'><a name="Page_79" id="Page_79">79</a></span> +that no such image is the primary factor in +exciting the instinctive reaction. For if it be +the actual presence of the female, or, in the +absence of such, a mental image, that renders +the pugnacious nature of the male responsive; +provided the usual stimulus were present, the +instinct ought surely to respond, not only under +one particular circumstance, but under all +circumstances. Yet, as we shall presently see, +a male is by no means consistently intolerant +of other males. It may be sociable at one +moment or pugnacious at another, but the +pugnacity is always peculiar to a certain +occasion—the occupation of a territory. What +shall we say then—that a mental image is a +situational item only when the territory is +occupied? It may be so; it may be that the +fact of occupation gives rise to the mental image +which, in its turn, renders the fighting instinct +explosive, which again renders the possession +of the territory secure. That such an interpretation +is possible we must all admit. But +if it were true, though it would not affect +the main consideration, namely, whether the +fighting has reference to the possession of a +particular female, or to the protection of the +territory, it would make further discussion as +to which of these is the condition of the fighting +unprofitable, for each would have its part to +play in the process, the territory remaining, +however, the principal factor in the situation.</p> + +<p>Now the difference in the times of arrival +of the male and female migrant varies in<span class='pagenum'><a name="Page_80" id="Page_80">80</a></span> +different species from a few days to a fortnight +or even more. It is most marked in those that +return to their breeding grounds early in the +season, and the greater the margin of difference +the greater scope is there for observation. In +my records for the past twelve years, there are +frequent references to these initial male contests in +the life of the Willow-Warbler and of the Chiffchaff; +and in the district which I have in mind, +these two species arrive early in the season, the +males preceding the females by a week or even +as much as a fortnight. Suppose, then, that two +Chiffchaffs establish themselves in adjoining +territories; or suppose that a male settles in a +territory already occupied; what is the result? +Well, scenes of hostility soon become apparent; +as the birds approach one another they become +more and more restive, their song ceases, they +no longer search for food in the usual methodical +manner, but instead their movements are hurried +and their call-notes are uttered rapidly—all of +which betrays a heightened emotional tone. +Then the climax is reached, there is a momentary +fluttering of tiny wings, a clicking of bills, and +for the time being that may be all. But unless +one or other of the combatants retires, this scene +may be repeated many times in the course of a +few hours, and repeated with varying degrees of +severity. Yet the fighting, even in the most +extreme form, when the birds locked together +fall slowly to the ground, is seldom of an +impressive kind, and one has to bear in mind +the capabilities of the actors, remembering that<span class='pagenum'><a name="Page_81" id="Page_81">81</a></span> +the most severe struggle might readily be interpreted +as a game if it were not for certain +symptoms which reveal its inner nature.</p> + +<p>The males of many other migrants can frequently +be observed to fight when there was +every reason to believe that females had still +to arrive. The Blackcap is notoriously pugnacious, +but not more so than the Marsh-Warbler +or the Whinchat. Here in Worcestershire, the +<i>Arundo phragmites</i> grows mainly on certain +sheets of water which are comparatively few +and far between, and the Reed-Warbler is +consequently restricted to isolated and more or +less confined areas. The males arrive early in +May before the new growth of reeds has +attained any considerable height, and each one +has its own position in the reed-bed, sings there, +and throughout the whole period of reproduction +actively resists intrusion on the part of other +males. I have kept watch upon a small area +of reeds daily from the date of the first arrival; +each individual was known to me, and as the +growing reeds were only a few inches in height, +a female could scarcely have escaped detection. +Yet time and again disputes arose, and males +pursued and pecked one another, striving to +attain that isolation for which racial preparation +had fitted them.</p> + +<p>But on account of their violence, or their +novelty, or because the absence of a female was +beyond question, some battles stand out in one's +memory more prominently than others. An +instance of this was a struggle between two<span class='pagenum'><a name="Page_82" id="Page_82">82</a></span> +Whitethroats which happened in the latter part +of April and lasted for three successive days. +The scene of its occurrence was more or less the +same on each occasion, and the area over which +the birds wandered was comparatively small. +The fighting was characterised by persistent +effort and was of a most determined kind, and +so engrossed did the assailants become that they +even fluttered to the ground at my feet. No +trace of a female was to be seen at any time +during these three days, nor, during the pauses +in the conflict, was the emotional behaviour of +a kind which led me to suppose that a female +was anywhere in the vicinity. And, if she had +been near, she must have made her presence +known, for the belief that she is a timid creature, +skulking on such occasions in the undergrowth, +is by no means borne out by experience.</p> + +<p>Even more impressive was a battle between +two male Cuckoos. It occurred high up in the +air above the tops of some tall elm-trees which +roughly marked the boundary line between their +respective areas, and the actions of the birds +were plainly visible. At the moment of actual +collision the opponents were generally in a +vertical position, and wings, feet, and beaks were +made use of in turn; one could plainly see them +strike at one another with their feet, and one +could observe the open bill which generally +denotes exhaustion, but may of course have been +due to anger, or used as a means of producing +terror. Yet no female appeared in the locality until +six days after the occurrence of this struggle—and<span class='pagenum'><a name="Page_83" id="Page_83">83</a></span> +she certainly is not easily overlooked, for her +note is unmistakable even when the behaviour of +the male does not betray her arrival.</p> + +<div class="figcenter" style="width: 500px;"><a name="f111" id="f111"></a><img src="images/fig111.jpg" width="500" height="756" alt="Male Cuckoos +fighting before the arrival of a female." title="Male Cuckoos fighting +before the arrival of a female." /></div> + +<p>That the actual presence of the respective +females exercised any influence on the course of +these struggles is more than doubtful. Not only +did one fail to detect them, but one's failure to +do so was confirmed by the knowledge that they +had not yet arrived in those particular localities. +Hence the fact of the male preceding the female +is a valuable aid to the interpretation of subsequent +behaviour; and one appreciates it the +more after having experienced the difficulty of +deciding whether she is present during the +conflicts between resident males, for no matter +how carefully we may observe the conditions +which lead up to, and which accompany, such +conflicts, or how closely we may scrutinise the +surrounding trees, undergrowth, or ground, there +always remains the possibility that she may, +after all, have been overlooked. But this must +not be taken to imply that in such cases direct +observation alone can lead to no serviceable +result, or that the evidence gained therefrom is +worthless. Far from it. Failure to detect a +female is so very common an occurrence that, +even if we lacked the corroborative evidence +supplied in the life of the migratory male, it +would still be unreasonable to suppose that it +were solely due to mistaken observation. We +mark her absence during the conflicts between +the respective males of many common species—the +Finches, Buntings, and Thrushes that occupy<span class='pagenum'><a name="Page_84" id="Page_84">84</a></span> +their territories early in the season when the +hedgerows and trees are still bare; but more frequently +amongst those that inhabit open ground, +because the movements of the birds are there +more accessible to observation. For instance, +half a dozen or more Lapwings can be kept in +view at the same time, and as they stand at dawn +in solitary state, keeping watch upon their respective +territories, they are conspicuous objects on +the short, frosted grass; no stranger can enter the +arena without the observer being aware of it, no +commotion can occur but one detects it, no +movement however small need be missed. And +so they fight, in a manner which leaves no doubt +as to the reality of the struggle, when their +prospective mates are absent not only from the +particular territories in which the conflicts take +place, but absent too from those adjoining.</p> + +<p>If the fact that males fight before they are +paired and in the absence of a female could be +placed beyond all question, it would no longer +be possible to regard her possession as the end +for which they are contending, and consequently +there would be no need to produce further +evidence. But the examples which I have given +refer, of course, to only a few migrants and a few +residents—and moreover it must be admitted +that a female <i>is</i> often conspicuous during the +battles—so that by themselves they must +be regarded, and rightly so, as inconclusive. +We must therefore pass on to consider evidence +of a somewhat different character.</p> + +<p>I spoke of the complexity of the strife. By<span class='pagenum'><a name="Page_85" id="Page_85">85</a></span> +this I mean that it is not merely a matter of +disputes between adjoining males, but that it +is a far more comprehensive business involving +both sexes. Thus female fights with female and +pair with pair, or a male will attack a female, or, +again, a pair will combine against a single male +or a single female. And from all this complexity +of strife we gain much valuable evidence +in regard to the question immediately before us. +For when one pair attacks another, or males +that are definitely paired fight with one another, +or an unpaired male attacks either sex of a +neighbouring pair indiscriminately, there is +surely little ground for supposing that the +possession of a mate is the reason of it all.</p> + +<p>The battles between pairs of the same species +are by no means uncommon. Observe, for +example, the central pair of three pairs of Reed-Buntings +occupying adjoining territories, and +keep a daily record of the routine of activity +practised by both sexes during the early hours +of the morning; then, at the close of the season, +summarise all the fighting under different headings, +and it will be found that the number of +occasions upon which the central pair attacked, +or was attacked by, neighbouring pairs will form +a considerable portion of the whole.</p> + +<p>Or watch the Moor-Hen, and for the purpose +choose some sheet of water large enough to +accommodate three or more pairs, and so situated +that the birds can always be kept in view. +Early in February the pool will be haunted +by numbers of individuals of both sexes, all<span class='pagenum'><a name="Page_86" id="Page_86">86</a></span> +swimming about together, and, if the pool is +surrounded by arable land, wandering over that +land subject to no territorial restrictions, apparently +free to seek food where they will. But as +time goes by, their number gradually decreases +until a few pairs only remain, and these will +occupy definite areas. If careful watch is then +kept and the relations of the pairs closely +studied, there will be no difficulty in observing +the particular kind of warfare to which I +am alluding, and it will be noticed that the +encounters are of a particularly violent description. +Thus two pairs approach one another, +and, when they meet, throw themselves upon +their backs, each bird striking at its adversary +with its feet or seizing hold of it with its beak; +and though, in the commotion that ensues, it is +almost impossible to determine what exactly is +happening, there is reason to believe that the +sexes attack one another indiscriminately.</p> + +<p>A struggle between two pairs of Pied Wagtails +is worth mentioning. It impressed itself +upon my memory because of the unusual vigour +with which it was conducted. The battle lasted +for fifteen minutes or more, and the four birds, +collecting together, pursued and attacked one +another—at one moment in the air, at another +upon the roof of a house where they would +alight and flutter about on the slates, uttering +their call-note without ceasing—until finally +they disappeared from view, still, however, continuing +the struggle.</p> + +<div class="figcenter" style="width: 500px;"><a name="f117" id="f117"></a><img src="images/fig117.jpg" width="500" height="756" alt="Two pairs of Pied Wagtails fighting +in defence of their territories." title="Two pairs of Pied Wagtails fighting +in defence of their territories." /></div> + +<p>Such is the nature of the warfare which<span class='pagenum'><a name="Page_87" id="Page_87">87</a></span> +prevails between neighbouring pairs, and which +can be observed in the life of many other +species—the Chaffinch, Stonechat, Blackbird, +Partridge, Jay, to mention but a few.</p> + +<p>The conflicts between males that are +definitely paired are of such common occurrence +that it is scarcely necessary to mention specific +instances. But the occasions on which a male +attacks either sex of a neighbouring pair indiscriminately, +or on which a pair combine to +attack a female, are less frequent.</p> + +<p>Now if it be true that males fight for no other +purpose than to gain possession of a mate, what +meaning are we to attach to the battles between +the pairs, or what explanation are we to give +of the fact that paired males are so frequently +hostile? Those who hold this view will probably +argue thus: "The presence of the female +is the condition under which the pugnacious +instinct of the male is rendered susceptible +to appropriate stimulation, and the stimulus +is supplied by a rival male; we admit that +all the fighting which occurs after pairing has +taken place has nothing to do strictly speaking +with gaining a mate, but, inasmuch as the +fact of possession is always liable to be challenged—and +no male can differentiate between a paired +and an unpaired intruder—we contend that it +would add to the security of possession if the +pugnacious instinct remained susceptible to +stimulation so long as there were any possibility +of challenge from an unpaired male; and we +think that the waste of energy involved in<span class='pagenum'><a name="Page_88" id="Page_88">88</a></span> +the struggles between paired birds, and which +we grant is purposeless, would be more than +balanced by the added security." This is a +possible explanation and requires consideration. +It cannot account for all the diverse ways in +which the sexes are mixed up in the fighting—it +cannot, for instance, explain the fact that an +unpaired male will attack either sex of an +adjoining pair indiscriminately—but nevertheless +it appears at first sight to be a reasonable +explanation of some of them. We must +remember, however, that fighting continues +throughout the whole period of reproduction. +Even after the discharge of the sexual function +has ceased, and the female is engaged in incubation +or in tending her young, the male is still +intolerant of intruders; and it is difficult to +believe that, at so late a stage in the process, a +female could be any attraction sexually to an +unpaired male. But apart from any theoretical +objection, there remains the fact—namely that +there is no evidence that a male, after having +once paired, is liable to be robbed of its mate. +And in support of this fact I have only to state +that I have met with no single instance of +failure to obtain and hold a mate when once a +territory had been secured. Bearing in mind +then that both sexes participate in the fighting, +and that individuals of the opposite sex frequently +attack one another; that all such +conflicts are characterised by persistent effort, +and that they are not limited to just the +particular period when the sexual instinct is<span class='pagenum'><a name="Page_89" id="Page_89">89</a></span> +dominant but continue throughout the breeding +season; bearing in mind that in at least one +form of this promiscuous warfare the influence +of the female can be definitely excluded, and +that, in the remaining forms, the evidence which +is required to link them up with the biological +end of securing mates is lacking—can it be +denied that the complexity of the strife makes +against the view that the possession of a female +is the proximate end for which the males are +fighting?</p> + +<p class="tb">We started with the most simple aspect of +the whole problem, the fighting of two males in +the presence of one female—the aspect upon +which attention has usually been fixed. And if +it remained at that, if observation failed to +disclose any further development in the situation, +then there would be no need to probe the +matter deeper, there would be no reason to +doubt the assertion that the quarrel had direct +reference to the female. But assuredly no one +can ponder over the diversity of battle and +still believe that the possession of a mate +furnishes an adequate solution of the mystery. +Clearly such an hypothesis cannot cover all +the known facts; there are conflicts between +separate pairs, and there are conflicts between +males when females are known to be absent and +when their mates are even engaged in the work +of incubation—these cannot be due to an +impulse in a member of one sex to gain or keep +possession of one of the other sex. So that +taking all these facts into consideration, we are<span class='pagenum'><a name="Page_90" id="Page_90">90</a></span> +justified, I think, in hesitating to accept this +view, and must look elsewhere for the real +condition under which the pugnacious nature of +the male is rendered susceptible to appropriate +stimulation.</p> + +<p>What then is the meaning of all this +warfare? The process of reproduction is a +complex one, built up of a number of different +parts forming one inter-related whole; it is +not merely a question of "battle," or of +"territory," or of "song," or of "emotional +manifestation," but of all these together. The +fighting is thus one link in a chain of events +whose end is the attainment of reproduction; +it is a relationship in an inter-related process, +and to speak of it as being even directly related +to the territory is scarcely sufficient, for it +is intimately associated with the disposition +which is manifested in the isolation of the +male from its companions, and forms therewith +an <i>imperium in imperio</i> from which our +concept of breeding territory is taken. But +let me say at once that it is no easy matter to +prove this, for since so many modes of behaviour, +which can be interpreted as lending support to +this view, are likewise interpretable on the view +that the presence of a female is a necessary condition +of the fighting, it is difficult to find just +the sort of evidence that is required. Nevertheless, +after hearing the whole of the evidence and +at the same time keeping in mind the conclusion +which we have already reached, I venture to<span class='pagenum'><a name="Page_91" id="Page_91">91</a></span> +think that the close relationship between the +warfare on the one hand and the territory on the +other will be fully admitted.</p> + +<p>Formerly I deemed the spring rivalry to +be the result of accidental encounters, and I +believed that an issue to a struggle was only +reached when one of the combatants succumbed +or disappeared from the locality, a view which +neither recognised method nor admitted control. +Recent experience has shown, however, that I +was wrong, and that there is a very definite +control over and above that which is supplied by +the physical capabilities of the birds.</p> + +<p>Let us take some common species, the +Willow-Warbler being our first example; and, +having found three adjoining territories occupied +by unpaired males, let us study the conflicts +at each stage in the sexual life of the three +individuals, observing them before females have +arrived upon the scene, again when one or two +of the three males have secured mates, and yet +again when all three have paired. Now we +shall find that the conditions which lead up +to and which terminate the conflicts are remarkably +alike at each of these periods. A male +intrudes, and the intrusion evokes an immediate +display of irritation on the part of the owner +of the territory, who, rapidly uttering its song +and jerking its wings, begins hostilities. Flying +towards the intruder, it attacks viciously, and +there follows much fluttering of wings and +snapping or clicking of bills. At one moment +the birds are in the tree-tops, at another in the<span class='pagenum'><a name="Page_92" id="Page_92">92</a></span> +air, and sometimes even on the ground, and +fighting thus they gradually approach and +pass beyond the limits of the territory. Whereupon +a change comes over the scene; the male +whose territory was intruded upon and who all +along had displayed such animosity, betrays +no further interest in the conflict—it ceases to +attack, searches around for food, or sings, and +slowly makes its way back towards the centre +of the territory.</p> + +<p>Scenes of this kind are of almost daily +occurrence wherever a species is so common, +or the environment to which it is adapted so +limited in extent, that males are obliged to +occupy adjacent ground. The Moor-Hen abounds +on all suitable sheets of water, and it is a bird +that can be conveniently studied because, as +a rule, there is nothing, except the rushes that +fringe the pool, to hinder us from obtaining a +panoramic view of the whole proceedings, and +moreover the area occupied by each individual +is comparatively small. Towards the middle of +February, symptoms of sexual organic change +make themselves apparent, and the pool is then +no longer the resort of a peaceable community; +quarrels become frequent, and as different +portions of the surface of the water are gradually +appropriated, so the fighting becomes more +incessant and more severe. Each individual +has its own particular territory, embracing a +piece of open water as well as a part of the rush-covered +fringe, within which it moves and lives. +But in the early part of the season, when the<span class='pagenum'><a name="Page_93" id="Page_93">93</a></span> +territories are still in process of being established, +and definiteness has still to be acquired, trespassing +is of frequent occurrence, and the +conflicts are often conspicuous for their severity.</p> + +<p>Now these conflicts are not confined to +unpaired individuals, nor to one sex, nor to +one member of a pair—every individual that +has settled upon the pool for the purpose of +breeding will at one time or another be involved +in a struggle with its neighbour. If then we +single out certain pairs and day by day observe +their actions and their attitude towards intruders, +we shall notice that, instead of their routine of +existence consisting, as a casual acquaintance +with the pool and its inmates might lead us +to believe, of an endless series of meaningless +disputes, the behaviour of each individual is +directed towards a similar goal—the increasing +of the security of its possession; and further, +if we pay particular attention to the circumstances +which lead up to the quarrels and the +circumstances under which such quarrels come +to an end, we shall find, when we have accumulated +a sufficient body of observations, that the +disputes always originate in trespass, and that +hostilities always cease when the trespasser +returns again to its own territory. By careful +observation it is possible to make oneself +acquainted with the boundaries—I know not +what other term to use—which separate this +territory from that; and it is the conduct of the +birds on or near these boundaries to which +attention must be drawn. A bird may be<span class='pagenum'><a name="Page_94" id="Page_94">94</a></span> +feeding quietly in one corner of its territory +when an intruder enters. Becoming aware of +what is happening it ceases to search for food, +and approaching the intruder, at first swimming +slowly but gradually increasing its pace, it +finally rises and attacks with wings and beak, +and drives its rival back again beyond the +boundary. Thereupon its attitude undergoes +a remarkable change; ceasing to attack, but +remaining standing for a few moments as if +still keeping guard, it betrays no further interest +in the bird with which a few seconds previously +it was fighting furiously. On one occasion I +watched a trespasser settle upon a conspicuous +clump of rushes situated near the boundary. +The owner, who was at the moment some +distance away, approached in the usual manner, +and, having driven off the trespasser, returned +immediately to the clump, where it remained +erect and motionless.</p> + +<p>A feature which marks all the fighting, and +which we cannot afford to disregard, is the +conative aspect of the behaviour of the owner of +the territory. The bird attacks with apparent +deliberation <i>as if</i> it were striving to attain some +definite end. I recollect an incident which was +interesting from this point of view. A pair of +Reed-Buntings were disturbed by a Weasel +which had approached their nest containing +young. Both birds betrayed symptoms of +excitement; as the Weasel threaded its way +amongst the rushes, so they fluttered from +clump to clump or clung to the stems, uttering<span class='pagenum'><a name="Page_95" id="Page_95">95</a></span> +a note which is peculiar to times of distress, and +followed it thus until finally it disappeared in +a hedge. The rapidly uttered note and the +excitement of the birds caused some commotion, +and the male from an adjoining territory +approached the scene. Now one would have +expected that the presence of this bird, and +possibly its aid in driving away a common +enemy, would have been welcomed; one would +have thought that all else would have been +subservient to the common danger, and that +so real a menace to the offspring would have +evoked an impulse in the parent powerful enough +to dominate the situation and subordinate all the +activities of the bird to the attainment of its end. +But what happened? Three times during this +incident, the male, whose young were in danger, +abandoned the pursuit of the Weasel and +pursued the intruder. It was not merely that +he objected to the presence of this neighbouring +male in a passive way, nor even that he had +a momentary skirmish with it, but that he +determinedly drove the intruder beyond the +boundary and only then returned to harass the +Weasel.</p> + +<p>Thus it seems clear that the proximate end to +which the fighting is directed is not necessarily +the defeat of the intruder, but its removal from a +certain position. And inasmuch as this result +will be obtained whether the retreat is brought +about by fear of an opponent or by physical +exhaustion, it is manifest that too much significance +need not be attached to the amount of<span class='pagenum'><a name="Page_96" id="Page_96">96</a></span> +injury inflicted. It is necessary to bear this in +mind, because it is held by some, who have +carefully observed the actions of various species, +that overmuch importance is attached to the +conflicts, that in a large number of instances +they are mere "bickerings" and lead to nothing, +and that they are now only "formal," which +means, I suppose, that they are vestigial—fragments +of warfare that determined the survival +of the species in bygone ages. But if the +conclusion at which we have just arrived be +correct, if we can recognise a single aim passing +through the whole of the warfare—and that one +the removal of an intruder from a certain +position, then we need no longer concern ourselves +as to the degree of severity of the battles—we +see it all in true perspective. Neither +exhaustion nor physical inability are the sole +factors which determine the nature and extent of +the fighting; there is a more important factor +still—position. According, that is to say, to the +position which a bird occupies whilst fighting is +in progress, so its pugnacious nature gains or +loses susceptibility, and it is this gain or loss of +susceptibility which I refer to when I speak of +the fighting as being controlled.</p> + +<p>What we have then to consider is the relation +of "susceptibility" to "position." We can +explain the relationship in two ways. We can +say that the part of the nature of the male which +leads to the occupation of a territory, and is +partly hereditary and partly acquired, is stronger +than the part which leads the bird to fight, and<span class='pagenum'><a name="Page_97" id="Page_97">97</a></span> +which is conditioned by the presence of a female, +and that consequently when the male passes the +boundary, the impulse to return asserts itself and +the conflict ceases; or we can say that the +occupation of a territory is the condition under +which the pugnacious instinct is rendered susceptible +to stimulation, that the stimulus is +supplied by the intruder, and that when the male +passes outside the accustomed area its instinct is +no longer so susceptible and it therefore retires +from the conflict.</p> + +<div class="figcenter" style="width: 500px;"><a name="f129" id="f129"></a><img src="images/fig129.jpg" width="500" height="409" +alt="Long-tailed Tit +Males fighting for possession of territory. The feathers +have been torn from the crown of the defeated and dying rival." title="Long-tailed Tit +Males fighting for possession of territory. The feathers +have been torn from the crown of the defeated and dying rival." /></div> + +<p>Of these explanations, the first is not altogether +satisfactory. It requires the presence of +a female and, as we have seen, a female is by +no means always present. Then it attributes to +the one side of the inherited nature an influence +which is not borne out by the facts, for in the +ordinary routine of existence, without the incentive +of battle, every individual is liable to wander +occasionally beyond its boundary and to intrude +temporarily upon its neighbours; and this it +could scarcely do, providing its nature to remain +within the territory were powerful enough to +dominate its movements and curtail its activities +even during the excitement of an encounter. +But there is nothing inherently improbable in +the alternative hypothesis, nor anything that +is at all inconsistent with the behaviour as +observed; on the contrary, if it is admitted, the +facts become connected together and exhibit a +meaning which they otherwise would not have +possessed.</p> + +<p>So much for the controlling influence of<span class='pagenum'><a name="Page_98" id="Page_98">98</a></span> +"position," which alone seems to me sufficient +ground for believing that the fighting has reference +to the territory. But it is not the whole of +the evidence.</p> + +<p>Now if it were possible to demonstrate by +actual observation that those males which had +not established territories were not pugnacious, +we should have something in the nature of proof +of the correctness of this view. Demonstrative +evidence of this kind is, however, unattainable. +Yet we can come very near to obtaining it by +reason of a peculiar feature which marks the process +of acquiring territory—the neutral ground. +The Lapwing will serve as an illustration. In +the previous chapter I referred to the small flocks +that appeared in the accustomed water meadow +early in February, and I described how they +settled day after day in that meadow, but only +in a limited part of it, where they passed their +time in rest, in preening their feathers, or in +running this way and that lazily searching for +food; and how, at length, the flock dwindled by +reason of individuals breaking away in order to +secure positions on the remaining part of the +meadow. Here the neutral ground is adjacent +to the territories, and, while still occupied by +the flock, is resorted to by the males that had +deserted that flock in order to establish those +territories.</p> + +<p>Suppose now that we have the whole +meadow in view from some point of vantage. +In front of us are the territories, in the distance +the neutral ground; and in each territory there<span class='pagenum'><a name="Page_99" id="Page_99">99</a></span> +is a solitary male, while on the neutral ground +a number of individuals of both sexes are +assembled, and move about freely one amongst +another. So that the scene presented to view +is somewhat as follows: a flat meadow, at one +end of which, and at fairly regular intervals, +a few solitary individuals are dotted about, each +one keeping at a distance from its neighbours; +while at the other end a number of individuals +are collected together in a comparatively small +space, apparently deriving some satisfaction from +their close association. That surely is a very +remarkable contrast. But let us continue our +investigation, first fixing our attention upon the +solitary individuals; one is standing preening its +feathers, another is squatting upon the ground, +a third runs a few yards in this direction then a +few yards in that, stimulated apparently by the +sight of food, and so on. Moreover, each one +keeps strictly to a well-defined area and makes +no attempt to associate with its fellows. One of +the males, however, whilst roaming backwards +and forwards approaches the limit of its territory, +and this brings the neighbouring bird, whose +boundary is threatened, rapidly to the spot. In +an upright position both stand face to face, and +the battle then begins; with their wings they +attempt to beat one another about the body, +with their beaks they aim blows at the head, +and in the mêlée wings and legs seem to be +inextricably mixed; whilst at intervals, driven +backwards by the force of the collision, they are +compelled to separate, only, however, to return to<span class='pagenum'><a name="Page_100" id="Page_100">100</a></span> +the charge—and the sound of beating wings and +the feathers that float in the air are tokens of +earnestness. Such scenes are of frequent occurrence; +but the conflicts vary in intensity, and +the circumstances under which they occur vary +too, and females come and go without leaving +any clue as to their ultimate intentions.</p> + +<p>Turning now to the flock one is impressed +with the friendship that seems to exist between +the various members. There are, it is true, +occasional displays of pugnacity which never +seem to develop into anything very serious; for +instance, one bird will fly at another, and a +momentary scuffle is followed by a short pursuit +but nothing more—nothing, that is to say, in +the least comparable with the battle previously +described. Of what is the flock composed? +Of members of both sexes. There is no difficulty +in assuring oneself that this is so. But is it +entirely composed of individuals in whom development +has not reached a stage adequate for the +functioning of the primary dispositions? No, +not entirely; for it will be observed that its +number is a fluctuating one, that birds come +and go, and, if a close watch is kept upon the +different individuals as they leave, it will be +noticed that some at least are inmates of the +territories at the opposite end of the meadow—the +solitary members whose behaviour we were +recently watching. This fact is an important +one. We were impressed, it may be remembered, +with the contrast between the general behaviour +of the birds at the opposite ends of the meadow.<span class='pagenum'><a name="Page_101" id="Page_101">101</a></span> +But now it appears as if the contrast were not +between this individual and that, but between +the behaviour of the same one under different +circumstances. The male, that is to say, which, +while in its territory, tolerates the approach of +no other male, flies to the flock and is there +welcomed by the very individuals with whom a +short time previously it had been engaged in +serious conflict.</p> + +<p>But if the conditions are reversed and the +flock happens to settle in an occupied territory, +the attitude of the owner towards the flock is +very different. In the year 1916 an incident +of this kind occurred in the meadow to which +reference has already been made. The weather +had been exceptionally severe—very cold easterly +and north-easterly winds, frost, and frequent +falls of snow had affected the behaviour of the +Lapwings, and seemed to have checked the +normal development of their sexual routine. +The males would attempt to establish themselves, +and then, when the temperature fell and +the ground was covered with snow, would collect +again in flocks and follow their winter routine. +It was on the 9th March, during one of the spells +of milder weather, that the flock on the neutral +ground was disturbed and settled mainly in +the territory marked No. 3 on the 1916 plan, +but partly on that marked No. 2. The owners +thereupon began to attack the different members +of the invading flock. Fixing attention upon a +particular bird whilst ignoring the remainder, +the No. 3 male drove it away, and then after<span class='pagenum'><a name="Page_102" id="Page_102">102</a></span> +a pause drove another away, and so on until +by degrees all the invaders were banished, and +the No. 2 male did likewise. The interest of +this incident lies, however, in the behaviour of +the different individuals of which the flock +was composed; when attacked they made no +real show of resistance, but accepted the situation +and left. The will to fight was clearly lacking, +yet their presence was a source of annoyance to +the owners of the territories. A short time +previously a female had accompanied one of +the males and was at that time somewhere in +the vicinity, but beyond this there was no +evidence to show that either of them were +paired, and even if the presence of the female +were the reason of the pugnacity of the one, +it could not well account for that of the +other.</p> + +<p>The neutral ground does not always happen +to be so close at hand as in the case of the +meadow referred to. Sometimes the birds will +resort to a particular field, attracted probably +by a plentiful supply of food, and here they +collect and behave as they do during the winter, +running this way and that as the fancy takes +them, meeting together by accident at one +moment, parting at another, according to the +direction in which they happen to wander. +Of animosity there is little sign; the season +might be the middle of winter instead of the +middle of March for all the indication there +is of sexual development, and yet one knows +that they will behave differently when they<span class='pagenum'><a name="Page_103" id="Page_103">103</a></span> +leave this ground, as presently they will, and +return to their territories in the surrounding +neighbourhood, and that there each one will +fight if necessary to preserve its acre from +intrusion.</p> + +<p>It would seem, then, from this that the +fighting must bear some relation to the +particular area of ground in which it occurs; +and unless it can be shown that there is some +other factor in the external environment of +the male, that is the direction in which we +must look for the condition under which the +instinct is rendered susceptible. One's thoughts +turn, of course, to the female, but she too passes +backwards and forwards between the territories +and the neutral ground, and if her presence +were really a <i>conditio sine qua non</i> of the strife, +one would like to know why, when she leaves +those territories and joins the flock and the +males do likewise, similar conflicts should not +prevail there also.</p> + +<p>Other species have their neutral ground, but +the environment seldom affords such facilities +for observation as does that of the Lapwing. +Even though the Moor-Hens, who are so +conspicuously intolerant upon the pool, <i>do</i> feed +together amicably upon the meadows adjoining; +and the Chaffinch that is so pugnacious in the +morning, <i>does</i> seek out the flock later in the +day; yet their conditions of existence prevent +our obtaining a panoramic view of the whole +proceeding, and we have to study each scene +separately before discovering that the relation<span class='pagenum'><a name="Page_104" id="Page_104">104</a></span>ship +between intolerance and the territory +on the one hand, and friendship and the +neutral ground on the other, is just as strong +a feature as it is in the behaviour of the +Lapwing.</p> + +<p>I shall now give a brief account of the +conduct of a male Reed-Bunting which by +persistent effort established itself late in the +season, and I shall do so because its behaviour +tends to confirm much that has been said in +the preceding pages.</p> + +<p>Early in March three male Reed-Buntings +occupied a small water meadow overgrown +with the common rush, and by the third week +all of them were paired. On the 30th March +two of the males were unusually pugnacious, +and on the following day fighting continued +and at times was very severe. Now I knew +that the occupants of the ground in which +the fighting was taking place were paired, +and not doubting that the combatants were +the owners of two territories marked for +convenience sake Nos. 1 and 2, I was at a +loss to understand the meaning of so determined +and persistent a struggle. My attention, however, +was presently drawn to a third bird, which +also joined in the conflict and made the whole +situation still more perplexing. This bird, as +it soon became clear, was none other than the +owner of No. 2 territory, and the one that +I had previously regarded as such was a new +arrival. On the following day, the 1st April, +fighting continued, and in my record for that<span class='pagenum'><a name="Page_105" id="Page_105">105</a></span> +day there is a note to the effect that "No. 2 +female seems to be of no interest to No. 5 +male (the new arrival); its purpose seems to be +to drive away intruders." On the 2nd April +and subsequent days, this bird attacked every +other male that approached, and not only +maintained its position but ultimately succeeded +in securing a mate. Here then we have two +territories occupied by two males, both of +which had obtained a mate. The relation of +these two birds was normal, a month's routine +had defined their boundaries, and conflicts were +less frequent than formerly. But upon this +comparatively peaceful scene a strange male +intrudes. Observe the manner of the intrusion. +The stranger does not wander about first in +this direction and then in that, but acts <i>as if</i> +it had some definite end in view, and establishing +itself in a small alder bush which it +uses as a base or headquarters, it gradually +extends its dominion, gains the mastery over +the surrounding ground, part of which belonged +to No. 1 male and part to No. 2, and finally +drives a wedge, so to speak, between the two +territories.</p> + +<p>How is its behaviour to be explained, and +why did its presence cause such commotion? +No one could have watched the gradual unfolding +of this incident day by day and not have been +impressed by the persistent endeavour with +which this male maintained its position in one +small part of the meadow. This is the first and +most important consideration. Then there is<span class='pagenum'><a name="Page_106" id="Page_106">106</a></span> +the attitude, also significant, which it adopted +towards the females; for I take it that, apart +from the question of territory, the explanation of +its intrusion must be sought in the necessity for +securing a mate—that it was attracted by the +presence of the females, and that the proximate +end of its behaviour was the possession of one of +them. But if there is one thing that emerges +from the facts more clearly than another it is +that the course of its behaviour was in no way +influenced by the presence or absence of either +of the females. My reasons for saying so are +the following: in the first place, it made no +attempt to pursue or to thrust its attention upon +either one or the other of them; secondly, it +even went so far as to attack and drive them +away when they approached too closely; and in +the third place, when an unpaired female did at +length appear, it adopted a different attitude and +forthwith paired. And bearing in mind that +these two females had already been with their +respective mates for some considerable time, and +that there was reason to believe that coition had +actually taken place, is it likely that any counter-attraction +would have proved successful in +tempting either of them away from its mate, or +probable, if they were the sole attraction, that +the intruding male would have been so persistent +in remaining? How very much simpler it is to +fit the pieces together, if for the time being we +ignore the female and fix our attention upon the +territory. Each item of behaviour then falls +into its proper place, and the fighting which<span class='pagenum'><a name="Page_107" id="Page_107">107</a></span> +seemed so perplexing and meaningless becomes +a factor of prime importance. First of all the +male arrives; then it establishes itself in a small +alder bush and advertises its presence by song; +next, by persistent effort in attacking the +neighbouring males, it frees a piece of ground +from their dominion; and finally, in proper +sequence, a female arrives, pairing takes place, +and reproduction is secured.</p> + +<div class="figcenter" style="width: 500px;"><a name="f141" id="f141"></a><img src="images/fig141.jpg" width="500" height="792" alt="A battle between +two pairs of Jays." title="A battle between two pairs of Jays." /></div> + +<p>How then does the whole matter stand? If +it were males only that engaged in serious +conflict, and if they fought only in the presence +of a female, the problem would resolve itself into +one simply of obtaining mates. But the warfare +extends in a variety of directions, it is not +confined to one sex, nor to unpaired individuals, +nor need the opponents necessarily be of the +same sex; it involves both sexes alike singly or +combined. Now the view that the biological +end of battle is, in its primary aspect, related +to the female, cannot, as we have seen, apply +to the conflicts between different pairs, and +only by much stretching of the imagination +can it be held responsible for the hostility that +males frequently display towards females or <i>vice +versa</i>. It is valid only for a certain form of +warfare. But that form represents, you will say, +a large proportion of the whole, which is true; +and so long as we ignore the remainder, we +might rest content in the belief that we had +solved the major part of the problem. But can +we ignore the remainder? Can we say that the +conflicts between paired males, for example, are<span class='pagenum'><a name="Page_108" id="Page_108">108</a></span> +simply offshoots of the pugnacious disposition, +and have no part to play in the process of +reproduction? They recur with marked persistency +season after season and generation after +generation; they are to be found in species +widely remote; they are frequent in occurrence; +and no one who had observed them and noted +the vigour with which they are conducted, could, +I think, conclude that they were meaningless—and +be satisfied. They must somehow be +explained. So that if anyone thinks fit to +maintain that possession of a mate is an adequate +explanation of part of the hostilities, it is clearly +impossible to regard all the fighting as a +manifestation of one principle directed towards +a common biological end.</p> + +<p class="tb">But wherever we extend our researches, we +find that the facts give precision to the view that +the occupation of a territory is the condition +under which the pugnacious instinct is rendered +susceptible to stimulation. The Lapwing, when +in its territory, displays hostility towards other +males of its own species, but when upon neutral +ground, treats them with indifference; the Chiffchaff +pursues its rival up to the boundary and is +then apparently satisfied that its object has been +achieved; the cock Chaffinch in March permits +no other male to intrude upon its acre or so of +ground during the early hours of the morning, +but for the rest of the day it joins the flock +and is sociable; the Herring-Gull resents the +approach of strangers so long as it occupies its +few square feet of cliff, but welcomes companions<span class='pagenum'><a name="Page_109" id="Page_109">109</a></span> +whilst it is following the plough—all of which +points to a relation between the territory and the +fighting. And this view has at least one merit—it +accounts for all the fighting no matter what +degree of severity may be reached or in what +way the sexes may be involved. The complexity +of the strife presents no obstacle; for if the +biological end of the fighting is to render the +territory, which has already been established, +secure from intrusion, each sex will have its +allotted part to play at the allotted time: thus +the battles between the males before females +appear on the scene will decide the initial +question of ownership; those between the +females will give an advantage to the more +virile members and insure an even distribution +of mates for the successful males; the constant +struggles between paired males will roughly +maintain the boundaries and prevent such +encroachment as might hamper the supply of +food for the young; and the co-operation of +male and female in defence of the territory will +be an additional safeguard. Each form of battle +will contribute some share towards the main +biological function of reproduction.</p> + +<p>Hitherto we have dealt principally with the +male. We have referred, it is true, to the fact +that the female co-operates with her mate in +order to drive away intruders, but beyond this, +we have made no attempt to trace what part, if +any, she plays in the whole scheme. We must +do so now.<span class='pagenum'><a name="Page_110" id="Page_110">110</a></span></p> + +<p>The various steps by which the territory is +not only established but made secure from +invasion, imply an inherited nature nicely +balanced in many directions—first of all the male +must be so attuned as to be ready to search for +a territory at the right moment; then it must +be capable of selecting a suitable environment; +and, having established itself, it must be prepared +to defend its area from a rival, and to resist +encroachment by its neighbours—and if it failed +in any one of these respects, it would run the +risk of failure in the attainment of reproduction. +Each individual has therefore to pass, so to +speak, through a number of sieves—the meshes +of which are none too wide—before it can have +a reasonable prospect of success. This being so, +we ask, in the first place, whether the female, +too, may not have an eliminating test to pass; +and in the second place, whether she may not +also assist in furthering the biological end of +securing the territory.</p> + +<p>Now the answer to the first of these +questions will be found to be in the affirmative. +Just as, in the securing of a territory, the ultimate +appeal is to the physical strength of the male, +so, in the course of her search for a mate, the +female may be called upon to challenge, or may +be challenged by a rival, and the issue is decided +by force. My attention was first drawn to this +fact by a struggle between two female Whitethroats, +which I have described elsewhere. The +scene of its occurrence was the corner of a small +osier bed occupied by one male, and the females<span class='pagenum'><a name="Page_111" id="Page_111">111</a></span> +that took part in it had only recently arrived, +but the male, an unpaired bird, had been in +possession of its territory for some days. The +sequel to this struggle, which was protracted and +severe, was the disappearance of both females, +the male being left without a mate for a further +ten days.</p> + +<div class="figcenter" style="width: 500px;"><a name="f147" id="f147"></a><img src="images/fig147.jpg" width="500" height="932" alt="The female Chaffinch shares in the defence +of the territory and attacks other females." title="The female Chaffinch shares in the defence +of the territory and attacks other females." /></div> + +<p>Numerous instances have since come under +my notice. Hen Chaffinches become so absorbed +that they fall to the ground and there continue +the struggle. Seizing hold of one another by +the feathers of the head, they roll from side to +side, and then, without relaxing their grip, lie +exhausted—the quickened heart-beat, altered +respiration, tightly compressed feathers and +partially expanded wings betraying the intensity +of the conflict.</p> + +<p>As the breeding season approaches, hen +Blackbirds grow more pugnacious. Individuals +that early in the year have frequented the same +spot daily and have even shown every sign of +friendship, become openly hostile. For two +years in succession I had an opportunity of +observing females under such conditions, and +of studying the gradual change in their relationship. +Each morning at break of day and for +some hours afterwards they could be seen in the +same place, one following the other as they +searched for food first in this direction and then +in that, as if they derived some special pleasure +from the fact of their companionship. Then a +change began to manifest itself. Indications of +animosity became apparent; one would run<span class='pagenum'><a name="Page_112" id="Page_112">112</a></span> +towards the other in a threatening attitude +and, in a half-hearted manner, peck at it; and +gradually the hostility grew, until the tentative +pecking developed into a scuffle and the scuffle +into a conflict.</p> + +<p>Much fighting also occurs between the +females of the Reed-Bunting, and likewise +between those of the Moor-Hen, and because +these two species are not only common but +inhabit respectively open stretches of marshy +ground or large sheets of water, the fighting can +be readily observed.</p> + +<p>Why do the females fight before they are +definitely paired? To obtain mates? This +certainly seems to be the obvious explanation +because any question of securing territory can +be excluded; yet if it be true that their sex is +numerically inferior, it is difficult to understand +the necessity for such strenuous competition. +But what is the condition under which the +pugnacious instinct of the female is rendered +susceptible to stimulation? It cannot be merely +the presence of a male ready to breed, for then +there would be endless commotion amongst the +flocks of Chaffinches or of Lapwings which in +March are composed of both sexes, including +even males that have secured territories. There +must be some other circumstance; and, judging +by experience, it is to be found in the territory—a +male, that is to say, in occupation of one, is +the condition under which the inherited nature +of the female is allowed free play. We must +bear in mind, however, that the competition<span class='pagenum'><a name="Page_113" id="Page_113">113</a></span> +between the males is very severe, that large +numbers probably fail to pass even this preliminary +test, and that only a proportion are in +a position to offer to the female the condition +under which her process can successfully run its +course; so that the presumption is—though it is +incapable of demonstration—that there is a competition +for such males each recurring season, +and that, on the average, the weaker females fail +to procreate their kind.</p> + +<p>But apart from any direct assistance she may +give in driving away intruders, does she in any +way help to further the biological end of reproduction? +This is a difficult question to answer, +and the suggestion I have to make can only +apply in those cases in which the territory is +occupied throughout the breeding season. +Much of the fighting between the males occurs +in her presence, and it must be admitted—though +it is difficult to speak with any degree of +certainty—that such fighting, taken as a whole, +bears the stamp of exceptional determination. +Let us then grant that the excitement of a male +does, under these circumstances, reach a higher +level of intensity, and let us see how this will +add to the security of the territory. The fact +that the male has established itself and obtained +a mate is not alone sufficient to accomplish the +end for which the territory has been evolved. +During the period between the initial discharge +of the sexual function and the time when +incubation draws to a close, much may happen +to prejudice the future of the offspring; there<span class='pagenum'><a name="Page_114" id="Page_114">114</a></span> +is always the possibility of invasion by an +individual whose development is backward or +which has been unsuccessful in making good +the first step, and, as we saw in the case of the +Reed-Bunting, a portion of the ground won +may be lost; there is always the danger of +gradual encroachment by neighbouring owners; +and there is even a possibility that a pair may be +so persistently harassed by more virile neighbours +as to forsake the locality permanently. If then +a male is to attain a full measure of success it +must be capable of keeping its boundaries intact +up to the time when the young are able to fend +for themselves, and consequently it is important +that its intolerant nature should remain susceptible +to stimulation throughout the greater part +of the season.</p> + +<p>Does the presence of a female serve to +promote this end? Now we know very little of +the influence exerted by one sex upon the other. +Professor Lloyd Morgan has suggested that the +male raises the emotional tone of the female, a +suggestion which seems to me in accordance +with the facts. There is reason to believe, however, +that the converse is also true—namely that +the excitement of the male reaches a higher level +of intensity when a female is present. Granting +then that his emotional tone is raised, how will +this affect the question? So great is the +difference of opinion as to the part that the +emotions play in furthering the life of the +individual that one hesitates to accept any +particular one. But it seems to be generally<span class='pagenum'><a name="Page_115" id="Page_115">115</a></span> +admitted that emotion adds to the efficacy of +behaviour, and this is the view of Professor +Lloyd Morgan. "Whatever may be the exact +psychological nature of the emotions, it may be +regarded," he says, "as certain that they introduce +into the conscious situation elements which +contribute not a little to the energy of behaviour. +They are important conditions to vigorous and +sustained conation." Therefore, if it be true +that the female raises the emotional tone of the +male, the result will be an increased flow of +energy into all the specific modes of behaviour +connected with reproduction, amongst which +those directly concerned in the securing and +defence of the territory will receive their share; +so that instead of a progressive weakening of +just those elements in the situation which make +for success, the level of their efficiency will be +maintained as a result of such reinforcement. +But the female becomes intolerant of her own +sex when she has discovered a male ready to +breed, and, later, assists her mate in resisting +intrusion; and by raising her emotional tone, he +may be the means of furthering more strenuous +behaviour on her part. Each member of the +pair would in this way contribute towards the +energy of behaviour of its mate, and hence add +indirectly to the security of the territory.</p> + +<p class="tb">It may be well to illustrate the foregoing +remarks. Suppose that there is a small piece of +woodland barely sufficient to hold three pairs of +Willow-Warblers, and suppose that the male and +female in the middle territory did not respond to<span class='pagenum'><a name="Page_116" id="Page_116">116</a></span> +one another's influence quite as readily as the +adjoining males and females, what would be the +result? The emotional tone of the central pair +would stand at a lower level of intensity; and, +since their congenital dispositions would lack the +necessary reinforcement, the birds would tend +to become less and less punctilious in keeping +their boundaries intact, whereas the adjoining +pairs, always on the alert and meeting with little +opposition, would encroach more and more and +gradually extend their dominion. And so, by +the time the young were hatched, the parents +would be in occupation of an area too limited in +extent to insure the necessarily rapid supply of +food, and would be compelled to intrude upon +the adjoining ground. But knowing how +routine becomes ingrained in the life of the +individual, knowing that for weeks this pair had +submitted to their neighbours, can we believe +that they would be capable of asserting their +authority and that the young would be properly +cared for? Or suppose that different pairs of +Kittiwake Gulls on the crowded ledges, or +different pairs of Puffins in the crowded burrows, +varied in like manner, would they all have +equal chances of rearing their offspring? The +struggle for reproduction is nowhere more severe +than amongst the cliff-breeding sea birds; it is +not for nothing that one sees Kittiwake Gulls, +locked together, fall into the water hundreds of +feet below and struggle to the point of exhaustion, +or, as has been reported, to the point of +death; it is not for nothing that Puffins fight<span class='pagenum'><a name="Page_117" id="Page_117">117</a></span> +with such desperation. And surely success will +be attained by that pair whose emotional tone +stands high and whose impulse to fight is therefore +strong, rather than to the ill-assorted couple.</p> + +<p>The argument, then, is briefly this. In the +spring, a marked change takes place in the +character of the males of very many species; +instead of being gregarious they either avoid one +another and become hostile, or, if their conditions +of existence require that they shall +still live together, they become irritable and +pugnacious. This change is made known to us +by the battles of varying degrees of severity +which are such a feature of bird life in the +spring; and since a female can commonly be +observed to accompany the combatants, the +possession of a mate appears at first sight to be +the proximate end for which the males are +contending. But when the circumstances which +lead up to the quarrels are investigated closely, +the problem becomes more difficult; for it is +not merely a question of males fighting in the +presence of a female, as is generally supposed to +be the case, but on the contrary there is a complexity +of strife which is bewildering—males +attack females or <i>vice versa</i>; female fights +with female; or a pair combine to drive +away another pair, or even a solitary individual +no matter of which sex. This complexity of +strife makes against the view that the possession +of a mate is the reason of the fighting. But an +even stronger objection is to be found in the fact<span class='pagenum'><a name="Page_118" id="Page_118">118</a></span> +that males are hostile when no female is present—and +hence we must seek elsewhere for the true +explanation.</p> + +<p>Now if the behaviour of a male be closely +observed, it will be found that its pugnacious +instinct gains or loses susceptibility according to +the position which it happens to occupy—when +its ground is trespassed upon, the impulse to +fight is strong; but when it crosses the boundary +it seems to lose all interest in the intruder. +Moreover, in some species, the male rejoins +the flock at intervals during the early part +of the season and for a time leads a double +existence, passing backwards and forwards +between its territory and the neutral ground. +Its behaviour under these circumstances affords +some valuable evidence, for the bird displays +little if any hostility when accompanying the +flock, yet when it returns to the ground over +which it exercises dominion, no male can +approach without being attacked. The conclusion, +therefore, seems to be inevitable, namely +that the actual occupation of a territory is the +condition under which the pugnacious nature of +the male is rendered susceptible to appropriate +stimulation.</p> +<hr /> +<p><span class='pagenum'><a name="Page_119" id="Page_119">119</a></span></p> +<h3>CHAPTER IV</h3> + +<h4>THE RELATION OF SONG TO THE TERRITORY</h4> + + +<p>If we listen to the voices of the Waders as, +in search of food, they follow the slowly ebbing +tide, we shall notice that each species has a +number of different cries, some of which are +uttered frequently and others only occasionally. +Not only so, but if we study the circumstances +under which they are uttered, we shall in time +learn to associate certain specific notes with +certain definite situations.</p> + +<p>The Curlew, when surprised, utters a cry +with which most of us, I suppose, are familiar; +but when with lowered head it drives away +another individual from the feeding ground, +it gives expression to its feelings by a low, +raucous sound, which again is different from +its cry when a Common Gull steals the <i>arenicola</i> +that has been drawn out of the mud with such +labour.</p> + +<p>Thus we come to speak of "alarm notes," +"notes of anger," "warning notes"—naming +each according to the situations which normally +accompany their utterance. And so, all species,<span class='pagenum'><a name="Page_120" id="Page_120">120</a></span> +or at least a large majority of them, have, in +greater or lesser variety, cries and calls which +are peculiar to certain seasons and certain +situations; and since on many occasions we +have indisputable evidence of the utility of +the sound produced—as when, upon the alarm +being given by one individual, the flock of +Lapwing rises, or when, in response to a +particular note of the parent, the nestling +Blackcap ceases to call—so are we bound to +infer that all the cries are, in one way or +another, serviceable in furthering the life of +the individual.</p> + +<p>But besides these call-notes, birds produce +special sounds during the season of reproduction—some +by instrument, others by voice, +others again by the aid of mechanical device. +And not only is this the case, but many +accompany their songs with peculiar flights, +such as soaring to a great height, or circling, +or floating in the air upon outstretched wings. +These special sounds and special flights are +those with which I now propose to deal, +including under the heading "song" all sounds +whether harsh or monotonous or beautiful, and +whether vocally or otherwise produced; and I +shall endeavour to show not only that they are +related to the "territory," but that they contribute +not a little to the successful attainment +of reproduction.</p> + +<p>The vocal productions are infinite in variety +and combination. At the one extreme we +have songs composed of a single note repeated<span class='pagenum'><a name="Page_121" id="Page_121">121</a></span> +slowly or rapidly as the case may be, whilst at +the other we have the complex productions +of the Warblers; and between these two +extremes, notes and phrases are combined and +recombined in ways innumerable. And just as +there is a rich variety of combination, so +there is a very wide variation in the purity +and character of the notes—some are harsh, +others melodious, some flute-like, others more +of a whistle, and others again such as can +only be likened to the notes of a stringed +instrument. Hence in variety of phrase combination +added to variety in the character of +the note, there is a possibility of infinite modes +of expression.</p> + +<p>If, in the latter part of May, we take up +a position at dawn in some osier bed, we listen +to songs which have reached a high degree +of specialisation, songs, moreover, which appeal +to us on account of their beauty; if, on the +other hand, we climb down the face of the +sea cliff, we hear an entirely different class of +songs—harsh, guttural, weird, monotonous +sounds, which, appeal to us though they may, +lack the music of the voices in the osier bed. +And just as, in the osier bed, we can recognise +each species by its voice, so we can distinguish +the "cackle" of the Fulmar, the "croak" of +the Guillemot, or the "grunt" of the Shag. +In the osier bed, however, there is considerable +variation in the song of different individuals +of the same species, so much so that we can +recognise this one from that; whereas on the<span class='pagenum'><a name="Page_122" id="Page_122">122</a></span> +cliff we cannot distinguish between the voices +of different individuals. And the more highly +developed the song, the greater the range of +variation appears to be; but notwithstanding +this—notwithstanding the fact that the pitch +may differ, the phrase combination may differ, +and the timbre may differ—the song remains +nevertheless specific. So that the two principal +features of "song," broadly speaking, are +"diversity" and "specific character."</p> + +<p>In contrast with the call-notes, the majority +of which can be heard at all times of the year, +the song is restricted as a rule to one season, +and that one the season of reproduction. It +is true, of course, that some birds sing during +the autumn, and, if the climatic conditions are +favourable, in the winter also, just as others +betray, in the autumn, symptoms of emotional +manifestation peculiar to the spring; but just as +the manifestation of the latter is feeble and +vestigial, so, too, does the song of the former +lack the vigour and persistency which is characteristic +of the spring. Again, in contrast with +the call-notes, which are common alike to both +sexes, song is confined to one sex—a peculiar +property of the males.</p> + +<p>Now all, I think, will agree that it must +serve some biological purpose—this at least +seems to be the conclusion to be drawn from the +two outstanding features of "diversity" and +"specific character"; and since the voices of +different individuals of the same species vary, it +has been suggested that, by creating a more<span class='pagenum'><a name="Page_123" id="Page_123">123</a></span> +effective pairing situation, it is serviceable in +furthering the life of the individual. I do not +propose at the moment to enquire whether this +doctrine be true, but rather to direct attention +to other ways in which the song may be +useful.</p> + +<p>Is the instinct susceptible to stimulation +under all conditions during the season of reproduction, +or only under some well-defined +condition? This is the question to which we +will first direct inquiry.</p> + +<p>Song in its full development belongs, as we +have seen, to the season of reproduction; it is +heard at the dawn of the seasonal sexual process, +and is the most conspicuous outward manifestation +of the internal organic changes which +ultimately lead to reproduction. These changes +would appear, at first sight, to be the primary +condition which renders the instinct susceptible +to appropriate stimulation. But while this is +true up to a point, in so far, that is to say, as +organic changes are a necessary antecedent of +all behaviour connected with the attainment +of reproduction, closer acquaintance with the +circumstances under which the instinct is allowed +full play leads to the belief that they are not +alone sufficient to account for the facts as +observed. In order to arrive at a decision we +must seek out the specific factors in the external +environment with which "song" is definitely +related.</p> + +<p>Some birds cross whole continents on their +way to the breeding grounds, others travel many<span class='pagenum'><a name="Page_124" id="Page_124">124</a></span> +miles, others again find suitable accommodation +in a neighbouring parish—nearly all have a +journey to perform, it may be short or it may be +long. The flocks of Finches gradually decrease +and we observe the males scattering in different +directions in search of territories; we watch the +summer migrants on their way—small parties +halting for a few hours in the hedgerows and +then continuing their journey, single individuals +alighting on trees and bushes and resting there +for a few minutes, and the constant passage of +flocks of various dimensions at various altitudes; +and we see Fieldfares, Redwings, and Bramblings +slowly making their way from the south and +the west to their homes in the far north. +Occasionally we hear their song, not the +emotional outburst customary at this season, +but, except in isolated cases, a weak and tentative +performance. Gätke speaks of the absence +of song on the Island of Heligoland, and refers +to the Whitethroat as one of the few migrants +that enliven that desolate rock with their melody. +On the other hand, many migrants that rest +temporarily on the Isle of May sing vigorously.<a name="FNanchor_5_5" id="FNanchor_5_5"></a><a href="#Footnote_5_5" class="fnanchor">5</a> +But on the whole there is, I think, no question +that the male whilst travelling to its breeding +grounds, and, even after its arrival, whilst in +search of a territory, sings but little—and that +little lacks the persistency characteristic of +the period of sexual activity. Yet, when a +suitable territory is eventually secured, the +nature of the bird seems to change; for, instead +<span class='pagenum'><a name="Page_125" id="Page_125">125</a></span> +of being silent and retiring, as if aware of some +end not fully attained, it not only makes itself +conspicuous but advertises its presence by a +song uttered with such perseverance as to +suggest that that end is at length attained. +Hence, in a general way, the instinct of song +seems to be related to the establishment of a +territory.</p> + +<p>Now the subsequent course of behaviour +tends to confirm this view. We have already +had occasion to refer to the fact that the males +of some species desert their territories temporarily +and join together on ground which is regarded +by the birds that associate there as neutral, and +that they do so not merely for the purpose of +securing food but because they derive some +special pleasure from the act of association, and +we shall find that the altered behaviour of the +male when it leaves its territory to seek food or +to join the flock is an important point for us +just now.</p> + +<p>Buntings desert their territories temporarily +and collect in flocks on the newly sown fields of +grain. Some of the males are single, others are +paired, and accompanied, it may be, by their +mates; they wander over the ground in search +of food, uttering their call-notes from time to +time, or, settling upon the hedges and trees +surrounding the field, rest there and preen their +feathers. But even though a male may be +surrounded by other males, even though it may +occupy a position where it is conspicuous to all +around, even though, that is to say, it is<span class='pagenum'><a name="Page_126" id="Page_126">126</a></span> +apparently in contact with just those stimulating +circumstances which will evoke a response when +it returns to its territory, yet it makes no attempt +to sing.</p> + +<p>Lapwings, when they resort to the neutral +ground, run this way and that in full enjoyment +of one another's companionship, behaving +as they do when they flock in autumn +and winter. Specific emotional manifestation +is, however, absent, and their actions seem to +be in nowise affected by the powerful impulse +which only a few minutes previously determined +their conduct, for of the characteristic +flight with its accompanying cry there is no +sign.</p> + +<p>Early in the season Turtle Doves often +collect from the surrounding country at certain +spots where their favourite food is abundant. +The croak of this Dove—its true song—is a +familiar sound during the summer, but in +addition the bird has a sexual note characteristic +of the race. I watched a flock of upwards of +one hundred on some derelict ground approximately +eight acres in extent. Here, in May, +the birds were attracted by the seeds of <i>Stellaria +media</i> which was growing in profusion. After +5 <span class="smcaplc">A.M.</span> there was continuous traffic between this +piece of ground and the surrounding neighbourhood, +a constant arrival and departure of single +individuals or pairs; and, as they fed, the sexual +note could be heard in all directions. Now some +of the males occupied territories close at hand, +and one could watch their passage to and fro;<span class='pagenum'><a name="Page_127" id="Page_127">127</a></span> +yet in no single instance did I hear the true song +uttered on the feeding ground, although the +moment a male returned to its territory its +monotonous croak could be heard, uttered moreover +with that persistence which is so marked +a feature of all song or of the sounds that +correspond to it.</p> + +<p>Thus it will be seen that, even after the +internal organic changes have taken place, +the instinct of song is not susceptible to +stimulation at all times and under all circumstances, +but only at certain specified times +and under special circumstances which can be +observed to correspond with the occupation of +the territory.</p> + +<p>In many species each male singles out +within its territory some prominent position +to which it resorts with growing frequency. +This position is an important feature of the +territory, and exercises a dominating influence +on the life of the bird. I have referred to it +as the "headquarters," and it may be a solitary +tree or bush, an outstanding mound or +mole hillock, a gatepost or a railing—anything +in fact that supplies a convenient +resting place so long as it fulfils one condition, +namely that the bird when it is there is conspicuous. +It need not, however, be a tree or a +mound or indeed anything upon which the +bird can perch, for there is reason to think +that the soaring flight undertaken at this +season by so many males, since it is generally +accompanied by the specific sexual sound,<span class='pagenum'><a name="Page_128" id="Page_128">128</a></span> +answers the same purpose as the topmost branch +of a tree.</p> + +<p>Now there is nothing in the external +environment to which the song is more +definitely related than to the "headquarters"—this +at least is the conclusion to be drawn from +the behaviour, and I will indicate the sort of +evidence upon which such conclusion is based. +There is, first of all, the persistency with which +the male resorts to the same tree, even to the +same branch, and, as it seems, solely for the +purpose of advertisement. We know by +experience the approximate routine of the +male's behaviour; we know where to seek it, +where to hear it, and when once we have +discovered its headquarters, we know that there +it will sing day after day for weeks or it may +be for months together—perhaps the most +striking feature of its behaviour at this season. +Next, we find that other trees, though made use +of, are not made use of to a similar extent for +the purpose of song. The area occupied varies +much according to the nature of the environment; +it is sometimes extensive, and seldom less +than half an acre or so in extent; but in most +instances it contains plenty of trees and bushes +which could, one would imagine, serve the +purpose of a "headquarters" just as well as the +particular one selected, and yet the bird, when +there, betrays no inclination to sing at all comparable +with that which can be observed when +it occupies its accustomed perch. Further +evidence is afforded in the behaviour of those<span class='pagenum'><a name="Page_129" id="Page_129">129</a></span> +species that make temporary excursions from +their territories. The male, on its return, flies +as a rule direct to its special tree and sings. +Sometimes, however, it settles upon the ground, +not unfrequently accompanied by the female, +and while there remains silent; but presently +rising from the ground and deserting its mate, +it flies to the headquarters and sings. Again, +nearly every male at one time or another in the +course of the season is aroused to action by the +intrusion of a rival. The emotional tone of the +owner of the territory is then raised, and the +intruder is pursued and attacked; but this alone +is not sufficient, it seems as if the chain of +instinctive activities, when once aroused by +appropriate stimulation, must pursue its course +to the end—and the end in such a case is only +reached and complete satisfaction only gained +when the bird has not merely returned to his +"headquarters" but has given vocal expression +to his emotion. Finally, we must bear in mind +these two facts, that the "headquarters" is +occupied solely by the male—it forms no part of +the life of the female—and that it is the male +only that sings.</p> + +<p>Many such subtle incidents of behaviour as +the foregoing can be perceived but not readily +described, and trifling though they may seem +to be in themselves, yet in the aggregate they +yield full assurance of a close relationship.</p> + +<p>The distant song of a male, or the presence +of an intruding male, have also stimulating +effects, though in somewhat different ways.<span class='pagenum'><a name="Page_130" id="Page_130">130</a></span> +The former evokes the normal reply, that is to +say the bird, if silent, is liable to utter a corresponding +reply; the latter arouses hostility into +which is infused much feeling tone, the bird +sings hurriedly while in pursuit of its rival, +and, which is more remarkable still, even in the +midst of an encounter. Both the normal reply +and the emotional song must be similar in +origin—different aspects of the same situation—and +both are clearly related to the other +male.</p> + +<p>The arrival of a female may also be followed +by an emotional outburst which can be heard +at intervals for some days; on the other hand, +the song may continue as before or, for a time, +entirely cease.</p> + +<p>To take the emotional outburst first. This +would appear to be susceptible of explanation +on the hypothesis that the voice contributes to +a more effective pairing situation; an hypothesis +which admittedly, at first sight, gains some +support from the fact that a second or a third +male is frequently present. But, in truth, the +presence of a second male makes the situation, +so far as the relationship between the song and +the female is concerned, all the more perplexing; +for, as we have already seen, the instinct of +pugnacity, when aroused by the appearance of +an intruder, is also liable to be accompanied by +a similarly extravagant song. On each occasion +the vocal effort is infused with much feeling +tone, and it would be impossible to point to +any one feature which is peculiar to only one<span class='pagenum'><a name="Page_131" id="Page_131">131</a></span> +occasion. The question therefore arises as to +whether the emotional outburst which we are +attributing to the arrival of a female may not +after all be due to the presence of an intruding +male. It may be so. But although I can recall +no single instance in which the presence of an +intruder could be definitely excluded, yet I +should hesitate to base upon this any broad +generalisation.</p> + +<p>When the normal course of the song is not +interrupted by the arrival of a female, when, +that is to say, the male still pursues the routine +to which he has all along been accustomed, +and still sings at stated intervals in stated +places with a voice that betrays no heightened +emotional tone, even though the song may +convey some meaning to the delicate perceptual +powers of the female, we have nothing to lay +hold upon which can be construed as an indication +of direct relationship between the song +and the presence of the female.</p> + +<p>The partial or complete suspension of the +song after pairing has taken place is the most +interesting, as it is the most noticeable, feature. +Not that it is by any means universal—if it +were so, some of the difficulties that beset the +path of interpretation would be removed, but +it is sufficiently widespread to demand explanation. +In nearly every case it is, however, +only temporary, the period during which the +male is silent varying from a few days to a +few weeks. The male Grasshopper-Warbler, +when it first reaches us, sings persistently, but<span class='pagenum'><a name="Page_132" id="Page_132">132</a></span> +when it is joined by a female a change becomes +apparent; instead of the incessant trill, there +are spasmodic outbursts of short duration, and +in the course of a few days the bird lapses into +a silence which may be broken for a short while +at dawn, or late in the evening, but is often +complete. More striking still is the change in +the case of the Marsh-Warbler, and the sudden +deterioration, or even suspension, of strains so +beautiful and so varied, at a moment, too, when +it might least be expected, at once arrests the +attention. The Reed-Warbler that had its +headquarters in a willow sang vigorously from +the middle of May until a female arrived on +the 20th June, when its voice was hushed, except +for occasional outbursts which lacked force +and were of short duration. When the Wood-Warbler +secures a territory it repeats its sibilant +trill with unwearying zeal, yet no sooner does +a mate appear than its emotion is manifested +in other directions. The Reed-Bunting is +vociferous during February and March; but +when a female arrives, periods of silence are +frequent and the instinct of the bird becomes +progressively less susceptible to stimulation. +After the manner of the race the male makes +temporary excursions from its territory accompanied +by his mate, and it is noteworthy that +when he returns and she is absent he sings, +but that the moment she joins him, or even +comes into sight, he is silent. In fact, in greater +or less degree, a change is noticeable in the +song of many resident and migratory species<span class='pagenum'><a name="Page_133" id="Page_133">133</a></span> +under similar circumstances, a deterioration so +marked that we learn by experience to regard +it as a certain indication of the arrival of a +mate.</p> + +<p>Thus it becomes clear that there are certain +specific factors in the external environment with +which the instinct can be definitely related, +and in the order of their importance they are +(1) the territory as a whole; (2) the headquarters; +(3) an intruding male; (4) the female.</p> + +<p>To what extent are these relationships interrelated? +Are they all mutually dependent upon +one another, or is there one which conditions the +remainder?</p> + +<p>In the first place it is evident that if a male +were not to establish a territory, no opportunity +would be afforded for making use of any special +post or for acquiring a habit in relation to it, +and so without further consideration we may +say that the connection between the song and +the headquarters, whatever it may be, is +primarily dependent upon the establishment of +a territory.</p> + +<p>Next, we have the fact that the distant voice, +or still more so the presence, of another male +has an exciting influence and evokes a corresponding +reply. Here we have a direct relationship, +and one which at first sight appears to +be exclusive of cross-correlation. But is it really +so; does no circumstance arise under which even +the proximity of a rival fails to evoke response? +The reply is not doubtful. Such a circumstance +<i>does</i> arise—when a male for one reason or another<span class='pagenum'><a name="Page_134" id="Page_134">134</a></span> +passes outside the limits of its accustomed area. +This aspect of behaviour has already been fully +discussed in connection with the question of +hostility, and everyone, I imagine, must by +now be pretty well familiar with the facts. +However, it does not often happen that we +are given such an aid to interpretation as is +vouchsafed to us in the altered behaviour of +the male when it joins the flock, and if, as +I believe, song and hostility are intimately +associated, forming part of an inter-related +whole which, for biological interpretation, has, +as its end, the attainment of reproduction, it +is not surprising that circumstances which lead +to the modification of the one should likewise +affect the other; I offer no apology, therefore, +for adverting to this aspect of behaviour once +again.</p> + +<p>Now a male may leave its territory for three +reasons—to pursue an intruder, to join the flock +on neutral ground, or to find the necessary means +of subsistence on other feeding grounds. On +each of these occasions it hears the song of, and +is in close contact with, other males; and if the +relationship of which we are speaking be really +exclusive of cross-correlation, its instinct ought +to respond with the customary freedom. But +what happens? A male pursues its rival, +betraying much emotion and singing extravagantly, +until the boundary is passed, when +emotion subsides and it is silent; or, it flies to +the flock on neutral ground, and, although +surrounded by the very males that a short time<span class='pagenum'><a name="Page_135" id="Page_135">135</a></span> +previously evoked response, is there unresponsive; +or again, it goes in search of food and collects +with other males bent on a similar errand, and +in presence of what we know would be an +exciting influence under other circumstances, +it nevertheless remains silent. Hence the +relationship between the song and a male rival +seems, as in the case of the headquarters, to +depend in the first instance upon the occupation +of a territory.</p> + +<p>So that the relationship between the song +and the territory as a whole is clearly of a +different order from that which obtains between +the song and the headquarters, or the song and a +male rival; for the first, as far as can be judged +by observation, is exclusive of, whilst the second +and the third involve, cross-correlation. How +are these facts to be explained? We have +already seen that it belongs to the nature of the +male during the season of reproduction to +establish itself in a definite place, and this action +is just as much a part of its hereditary nature as +the building of the nest is of that of the female, +and it is just as necessary for the successful +attainment of reproduction. What exactly the +stimulus is to this mode of behaviour we do +not know; we can go no further back than +the internal organic changes which are known +to occur and which we assume, not without +some reason, are responsible for its initiation. +Granting, then, that there is this congenital +disposition, what relation does it bear to the +song? Without a doubt the song is likewise<span class='pagenum'><a name="Page_136" id="Page_136">136</a></span> +founded upon a congenital basis; it is truly +instinctive, and as such requires appropriate +stimulation; furthermore the male sings only +when in occupation of its territory. Having +regard to these two facts we might say that +the territory is the stimulus to the song. But +this can scarcely be a true interpretation, for +inasmuch as the stimulus would be relatively +constant, a relatively constant response ought to +follow, and even a slight acquaintance with the +daily round of behaviour will furnish plenty of +evidence to the contrary, seeing that the song, +though persistent, is never continuous—in fact +there are long periods of silence during the +daytime, and only in the morning and the +evening does the male become really vociferous. +What then is the stimulus? Through awareness +of something in the environment the male +responds to stimulation, and the only reply we +can give is that the headquarters, or a distant +song, or the proximity of another male—with +all of which, as we have seen, the instinct is +definitely related—are the specific factors which +normally evoke response—and experience teaches +us that the periods of quiescence are just those +when life is at its lowest ebb and these stimulating +factors less in evidence. Bearing this in +mind, bearing in mind the fact that when a male +joins the flock or crosses the boundary its +instinct ceases to respond, bearing in mind, +that is to say, that there is evidence of relationship +between these specific factors and the +song only when the territory is actually occu<span class='pagenum'><a name="Page_137" id="Page_137">137</a></span>pied, +the conclusion seems inevitable that we +have here the determining condition which +renders the instinct susceptible to appropriate +stimulation.</p> + +<p>There remains the female. I place her last +in order of importance, not because I regard her +influence as of small consequence, but because +the evidence is of a varied and complex kind, +so much so that it is difficult to ascertain by +observation just how far she is a situational item. +It will be remembered that the only direct +evidence we had of such influence was a +deterioration or, in some instances, a complete +cessation of vocal manifestation. Clearly then +we are confronted with a relationship of a +different kind from that which we have been +discussing; for not only is anything in the +nature of stimulation absent, but, and this is a +remarkable fact, the other items in the environment +which formerly evoked response no longer +do so in quite the same way. Is there any +awareness on the part of the male of the relation +between his voice and the mate that is to be, or +is it merely that as the sexual situation increases +in complexity some inhibiting influence comes +into play? These are questions which lead up +to difficult problems. But it is no part of my +task to discuss the psychological aspect of the +behaviour; my purpose is merely to show that +the situation on the arrival of a female undergoes +marked modification, that the instinct of the +male is then less susceptible to stimulation, and +that the factors in the external environment<span class='pagenum'><a name="Page_138" id="Page_138">138</a></span> +which formerly elicited response become relatively +neutral.</p> + +<p>Hence the appearance of the female on the +scene marks the opening of a new stage in the +life-history of the male, and, to judge by the +course of events, it would seem as if the song +with its network of relationships had now served +its main biological purpose.</p> + +<p>And now, what is the purpose, and what the +origin, of song? Is it, as some naturalists have +conceived, a means of raising the emotional tone +of the female, of creating a more effective pairing +situation, and so of removing a barrier to the +successful discharge of the sexual function; or, +is the emphasis here too much upon the +emotional, too little upon the strictly utilitarian, +aspect? All, I think, will agree that it must +serve some biological purpose, and the position +we have so far reached is that the determining +condition of its manifestation is not merely the +establishment, but the actual occupation of a +territory, and that there are no factors in the +external environment which can evoke response +in the absence of such condition. This being so, +the further questions arise as to whether it +contributes towards the attainment of the end +for which the whole territorial system has been +built up, and what precisely is the way in which +it does so.</p> + +<p>Everyone knows that in the spring the +shyest of birds no longer practise the art of +concealment. The Curlew soars to a great +height, and upon outstretched wings hovers in<span class='pagenum'><a name="Page_139" id="Page_139">139</a></span> +the air whilst uttering its plaintive wail; the +cock Grouse, as if dissatisfied with its "crowing," +springs into the air and becomes a conspicuous +object of the moor; the wary Redshank, poised +on flickering wings, forgets its mournful alarm +cry, and finds again its melodious song; and +even the secretive Grasshopper-Warbler crawls +out of the midst of the thicket in order to "reel," +just as, for a similar reason, Savi's Warbler +climbs to the top of a tall reed. In fact the +males of most species, when they are finally +established on the breeding grounds, make +themselves as conspicuous as possible by sight +and by sound. And since the sounds produced +by no two species are exactly alike, the females +are able to recognise their prospective mates, +and the males that are still in search of ground +have ample warning if that upon which they are +treading is already occupied. So that you see, +from the remarkable development of the vocal +powers in the male, there follow two important +results—"recognition" and "warning."</p> + +<p>We here turn from song as the expression of +an instinctive disposition, and the question of +what calls forth this expression, to the impression +produced by the song on the hearer.</p> + +<p>Most birds have a call-note or a number of +call-notes, which, generally speaking, are specifically +distinct. But to the human ear they are not +always so, perhaps because our power of hearing +is less sensitive than that of a bird, and unable to +appreciate delicate differences of tone. Be this +as it may, however, the fact remains that we<span class='pagenum'><a name="Page_140" id="Page_140">140</a></span> +often find it difficult, and in not a few cases +impossible, to recognise a bird merely by its call. +The plaintive notes of the Willow-Warbler and +of the Chiffchaff are to our ears very closely +akin, so, too, are those of the Marsh-Warbler +and of the Reed-Warbler, and there is a great +resemblance between the hissing sound produced +by the two Whitethroats. In Co. Donegal I +have been deceived by the spring-call of the +Chaffinch which, owing possibly to the humidity +of the atmosphere, is, there, almost indistinguishable +from the corresponding note of the +Greenfinch. The Yellow Bunting and the Cirl +Bunting frequently make use of a similar note, +so do the Curlew and the Whimbrel. In fact, +numberless instances could be quoted in which +notes appear to us identical, and, as a rule, the +more closely related the species, the more difficult +it becomes to distinguish the sounds—alike in +plumage, alike in behaviour, alike in emotional +manifestation, it would be surprising if they were +not alike in voice. But the moment we pass +from the call-notes to a consideration of the +songs we are faced with a very remarkable fact, +for not only are these readily distinguished, but +in many cases they bear no resemblance in any +single characteristic. What could be more unlike +than the songs of the Willow-Warbler and of +the Chiffchaff, of the Marsh-Warbler and the +Reed-Warbler, or of the Yellow Bunting and +the Cirl Bunting?</p> + +<p>Now when different individuals collect in +flocks at certain seasons, they assist one another<span class='pagenum'><a name="Page_141" id="Page_141">141</a></span> +in finding food, and afford mutual protection by +giving timely warning of the approach of a +common enemy, and the gregarious instinct is +thus of great advantage to the species; but no +matter how powerful the impulse to flock might +be, if there were no adequate means of communication, +the different units would frequently +fail to discover their neighbours. Here the +specific cries and calls come into play, enabling +them as they move about in search of food, or +change their feeding grounds, or whilst they are +on migration, to keep constantly in touch with +one another; and hence one purpose that these +call-notes serve is that of recognition. Moreover, +they convey their meaning to individuals of other +species and are acted upon, and are thus in every +sense socially serviceable; but on the other hand, +whilst there is much evidence to show that the +song is of great individual value, there is none +to show that it is in any like manner of direct +advantage to the community.</p> + +<p>If, then, there is in the call-notes an adequate +means of communication and of recognition, why +do I suggest that the song has also been evolved +primarily for the purpose of recognition?</p> + +<p>What, first of all, are the conditions in the +life behaviour during the season of reproduction +that make the intervention of the voice a consideration +of such importance? The general +result of our investigation might be summed up +thus: we found that the male inherits a disposition +to secure a territory, that at the proper +season this disposition comes into functional<span class='pagenum'><a name="Page_142" id="Page_142">142</a></span> +activity and leads to its establishment in a +definite place, and that it cannot search for a +mate because its freedom of action in this respect +is forbidden by law; that the female inherits no +such disposition, that she is free to move from +place to place, free to satisfy her predominant +inclination, and to seek a mate where she wills; +and, since the appropriate organic condition +which leads to pairing must coincide with +appropriate conditions in the environment, that +the union of the sexes must be accomplished +without undue delay. Furthermore we found +that a territory is essential if the offspring are to +be successfully reared; that, since the available +breeding ground is limited, competition for it is +severe, and that the male is precluded from +leaving the ground which he has selected, and +is obliged, in order to secure a mate, to make +himself conspicuous. That was our general +result. Now there are two ways by which the +male can make himself conspicuous—by occupying +such a position that he can be readily seen, or +by producing some special sound which will be +audible to the female and direct her to the spot. +The former, by itself, is insufficient; in the dim +light of the early dawn, when life is at its highest, +and mating proceeds apace, what aid would it be +for a male to perch on the topmost branch of a +tree, how slender a guide in the depth of the +forest? But whether in the twilight or in the +dark, in the thicket or the jungle, on the mountain +or on the moor, the voice can always be +heard—and the voice is the principal medium<span class='pagenum'><a name="Page_143" id="Page_143">143</a></span> +through which the sexes are brought into +contact.</p> + +<p>Well now, we come back to the question, +why, if all species have a serviceable recognition +call, that call should not be sufficient for the +purpose, just as, without a doubt, it is adequate +for all purposes at other seasons? The answer +is, I think, clear. The recognition call is not +confined to one sex, nor only to breeding birds; +it is the common property of all the individuals +of the species, and if the female were to rely +upon it as a guide she might at one moment +pursue another female, at another a non-breeding +male; she might even be guided to a +paired female or to a paired male, and time +would be wasted and much confusion arise. So +that no matter how much a male might advertise +himself by cries and calls which were common +alike to all the individuals of the species, it +would not assist the biological end which we +have in view. Something else is therefore +required to meet the peculiar circumstances, +some special sound bearing a definite meaning +by which the female can recognise, amongst the +host of individuals of no consequence to her, +just those particular males in a position to breed +and ready to receive mates. Hence the vocal +powers, the power of producing sounds instrumentally, +and the power of flight, have been +organised to subserve the biological end of +"recognition."</p> + +<p>And this view is strengthened, it seems to +me, by the erratic behaviour of certain species,<span class='pagenum'><a name="Page_144" id="Page_144">144</a></span> +more particularly by one remarkable case, the +case of the Cuckoo. The male, after having +established himself, utters his call persistently +from the day of arrival until approximately the +middle of June; but, in contrast with the +large majority of species, the female has a +characteristic call which she, too, utters at +frequent intervals. The female is polyandrous +and has a sphere of influence embracing the +territories of a number of males; she wanders +from place to place, is often silent, and not +unfrequently is engaged in dealing with her egg +or in searching for a nest in which to deposit it, +and therefore she is not always in touch with a +male, still less with any particular one. Now +there is much evidence to show that the +discharge of the sexual function amongst birds +is subject to control, and that this control +operates through the female—through her +physiological state becoming susceptible to +stimulation only at certain periods. So that we +have these considerations, that the female is +polyandrous, that she has a territory distinct +from that of the male, and that her sexual +impulse is periodical; and the further consideration +that the impulse, since it is periodical, is of +limited duration and must receive immediate +satisfaction. Such being the circumstances of +the case, would the voice of the male serve to +insure the union of the sexes at the appropriate +moment? Well, the fact that she is polyandrous +implies that every male in her sphere of +influence is not always capable of satisfying her<span class='pagenum'><a name="Page_145" id="Page_145">145</a></span> +sexual instinct. Is, then, the male's call an +indication of his readiness to yield to stimulation? +Without a doubt it is an index of the +general physiological state which generates the +sexual impulse, without a doubt it denotes a +general preparedness to breed, but there is no +evidence to show that it denotes the degree of +ardour of the male at any particular moment, +and much that proves the contrary. So that +only by the female producing some special +sound which will attract the males that are +eager and bring them rapidly to the spot where +she happens to be, only thus is it possible to +insure the consummation of the sexual act. +This, it seems to me, is the purpose of the +peculiar call of the female—a call which, so far +as biological interpretation is concerned, is just +as much a song as the melody of the Marsh-Warbler—and +its interest for us just now lies in +this, that here we have a special case in which +the sexes have separate territories, the female is +polyandrous, and the voice of the male is not +sufficient by itself to bring to pass the union +of the sexes; and in which, consequently, if +the purpose of song be that of recognition, +we should expect to find, as we do find, that +the female had a distinct and penetrating +call.</p> + +<p>We now come to the question of "warning," +by no means the least important purpose of +song. I pointed out that one of the chief +differences between the call-notes and the song +was that the former were socially serviceable,<span class='pagenum'><a name="Page_146" id="Page_146">146</a></span> +whereas the latter was only serviceable to +certain individuals; and in making this statement, +I had in mind the direct benefits to the +community which proceeded from an appreciation +of sounds having a mutually beneficial +meaning, not the indirect, though none the less +beneficial, consequences to the species as a +whole. Biologically considered, song, if it acts +as a warning and thereby leads in one way or +another to more complete success in the rearing +of offspring, may be spoken of as socially +serviceable; but it is legitimate to draw a +distinction between the prospective value of +remote relationships which we can foresee, +and the mutual assistance which the individuals +of a community derive from their close +association.</p> + +<p>If there were always sufficient breeding +ground to support the offspring of all the +individuals of each species, if the individuals +were always so distributed that there was no +possibility of overcrowding in any particular +area, and if the conditions of existence of +different species were so widely divergent that +the presence of this one in no way affected the +interests of that, no opportunity would be +afforded for the development of so complex a +system as is involved in the "territory" and all +that appertains to it. But the available breeding +ground is by no means unlimited. The +supply of food, which is a determining factor +in the environment, is always fluctuating according +to the climate and according to the changes<span class='pagenum'><a name="Page_147" id="Page_147">147</a></span> +in the earth's surface; and so the distribution of +the bird population in any given area, though it +may be suitably adjusted for one year or even +for a period of years, is bound in the course of +time to require readjustment. Now there +cannot be readjustment without competition, +nor competition without combat. But the +appeal to physical force is only a means to an +end, and, since no male can endure incessant +warfare and the perpetual strain of always being +on the alert, without experiencing such physical +exhaustion as might affect his power of reproduction, +its direct effect upon the combatants +cannot be otherwise than harmful—in fact it is +a necessary evil which for the good of the +species must be kept strictly within bounds. +Bearing in mind, then, these two facts, namely +that the distribution of the males is never stable +and that overmuch fighting may defeat the end +in view, we can appreciate the importance of +any factor which will lead to a more uniform +distribution and at the same time insure security +by peaceable means.</p> + +<p>The proximate end of the male's behaviour is +isolation—how is it to be obtained? If, after +having occupied a territory, the bird were to +remain silent, it would run the risk of being +approached by rivals; if, on the other hand, it +were merely to utter the recognition call of the +species, it would but attract them. In neither +case would the end in view be furthered, and +isolation would solely depend upon alertness and +the capacity to eject intruders. Supposing,<span class='pagenum'><a name="Page_148" id="Page_148">148</a></span> +however, that the song, just as it serves to +attract the females, serves to repel other males, +a new element is introduced deserving of recognition; +for those males that had established +themselves would not only be spared the +necessity of many a conflict, but they would be +spared also the necessity of constant watchfulness, +and so, being free to pursue their normal routine—to +seek food, to rest, and, if migrants, to +recover from the fatigue of the journey, they +would be better fitted to withstand the strain of +reproduction; and those that were still seeking +isolation in an appropriate environment, instead +of settling first here and then there only to find +themselves forestalled, would avoid and pass by +positions that were occupied, establishing themselves +without loss of time in those that were +vacant. Without the aid of something beyond +mere physical encounter to regulate dispersal, +it is difficult to imagine how in the +short time at disposal anything approaching +uniformity of distribution could be obtained. +Hence, both in the direction of limiting combat, +of insuring accommodation for the maximum +number of pairs in the minimum area, and of +conserving energy, the song, by conveying a +warning, plays an important part in the whole +scheme.</p> + +<p>And if this be so, if the song repels instead +of attracting, it follows that the more distinct +the sounds, the less likelihood will there be of +confusion; for supposing that different species +were to develop similar songs, whole areas might<span class='pagenum'><a name="Page_149" id="Page_149">149</a></span> +be left without their complement of pairs just +because this male mistook the voice of that, +and avoided it when there was no necessity for +doing so. So that just as from the point of +view of "recognition" each female must be able +to distinguish the voice of its own kind, so +likewise the warning can only be adequate +providing that the sounds are specifically distinct. +A point, however, arises here in regard to +closely related forms. Some species require +similar food and live under similar conditions of +existence; they meet in competition and fight +with one another; and, if they did not do so, the +food-supply of a given area would be inadequate +to support the offspring of all the pairs inhabiting +that area. Generally speaking, the more closely +related the forms happen to be, the more severe +the competition tends to become; and it may be +argued that in such cases a similar song would +contribute to more effective distribution and in +some measure provide against the necessity of +physical encounter; that, in fact, it would stand +in like relation to the success of all the +individuals concerned, as does the song to the +individuals of the same species. But we must +bear in mind that the primary purpose of song +is to direct the females to those males that +are in a position to breed; and to risk the +possibility of prompt recognition in order that +the males of closely related species should fight +the less, would be to sacrifice that which is +indispensable for a more remote and less +important advantage.</p> + +<p><span class='pagenum'><a name="Page_150" id="Page_150">150</a></span>What meaning does the song convey to a +male that is unestablished? Does the bird +recognise that it is forestalled; does it foresee +and fear the possibility of a conflict, and +conclude that the attempt to settle is not worth +while? I do not imagine that it thinks about it +at all. How then does the warning warn? +We will endeavour to answer this question, but, +in order to do so, we must review the stages by +which a territory is secured.</p> + +<p>We take as our starting point the internal +organic changes which are known to occur. +These changes are correlated with other changes, +manifested by a conspicuous alteration in +behaviour—to wit, the disappearance of sociability +and its replacement by isolation. Having +found a station which meets the requirements of +its racial characteristics, the male establishes +itself for a season, becomes vociferous, displays +hostility towards others of its kind, and in due +course is discovered by a female. The whole is +thus an inter-related whole, a chain of activities +which follow one another in ordered sequence. +Now we have seen that it is neither pugnacious +nor vociferous until the territory is actually +occupied; we have seen that the fact of occupation +is the condition under which the instincts of +pugnacity and of song are rendered susceptible +to appropriate stimulation; we have discussed +the nature of the stimulus in each case, and we +wish to know the sort of meaning that the song +conveys to an individual which is still in the +preliminary stage of seeking a station. In<span class='pagenum'><a name="Page_151" id="Page_151">151</a></span> +sequential order we have the following: (1) +internal organic changes which lead to isolation, +(2) the appropriate environment which gives rise +to an impulse to remain in it, (3) the occupation +of a territory which is the condition under which +the instincts are rendered susceptible to stimulation, +(4) the various stimuli. Each is dependent +upon that which precedes it, and no part can be +subtracted without failure of the biological end +in view, neither can the different stages be +combined in different order. So that, in +considering the significance of song to an +unestablished male, we are dealing with the +situation at a point at which all the latent +activities have not been fully felt, for all that so +far has occurred is the change from sociability to +isolation determined by internal organic changes. +The bird has not established a territory because +it has not come into contact with the appropriate +environment, and it is not pugnacious because +the condition which renders its instinct susceptible +is absent; and so, as it wanders from place +to place and hears the voices of males here or +males there, it merely behaves in accordance +with that part of its nature which predominates +just at that particular moment—the impulse to +avoid them.</p> + +<p>But given the appropriate environment, +given, that is to say, just that combination of +circumstances which might bring into functional +activity all the latent instincts of the intruder, +and no matter how vociferous the occupant of +a territory might be, it would not be preserved<span class='pagenum'><a name="Page_152" id="Page_152">152</a></span> +from molestation. The advantage of the song, +biologically considered, is then this, that it will +often prove just sufficient to preclude males +in search of isolation from coming into contact +with the environmental conditions adequate to +supply the stimulus to their latent activities +and to convert them into rivals.</p> + +<p>If this interpretation be correct, if we are +right in attributing the withdrawal solely to +the fact that the first stage only in the relational +series has been reached, it follows that the +effect of song upon males that have reached +subsequent stages in that series must be of a +very different kind. We have dealt with the +male when in the preliminary stage of seeking +isolation, we must deal with it now when +eventually it occupies a territory. How does +it behave when it hears, as it is bound to do, +the voices of rivals in its neighbourhood? You +may remember that some allusion was made +to the fact that an outburst of song from one +individual was followed, not unfrequently, by a +similar outburst on the part of other individuals +in the immediate locality. For example, silence +may reign in the reed-bed except for an occasional +note of the Reed-Warbler or Sedge-Warbler. +Suddenly, however, a dispute arises between two +individuals, accompanied by a violent outburst +of song, and forthwith other males in the +vicinity begin to sing excitedly and continue +doing so for some minutes in a strangely +vigorous manner, the tumult of voices affording +a striking contrast to the previous silence.<span class='pagenum'><a name="Page_153" id="Page_153">153</a></span> +Spasmodic outbursts of this kind, stimulated +by an isolated utterance, are by no means +uncommon. But not only does song stimulate +song; under certain conditions it has the still +more remarkable effect of arousing hostility. +The boundary that separates two adjoining +territories is by no means a definite line, but +rather a fluid area wandered over by this +owner at one moment, by that at another. +Now so long as the bird is silent while in this +area, the probability is that it will escape +detection and remain unmolested; let it however +sing—it often does so—and it will not merely +be approached but attacked, and consequently +this area is the scene of much strife. The point +to be noticed here is that the song brings about +no withdrawal; it elicits a response, attracts +instead of repelling, and, in short, arouses the +impulse that is always predominant in the +nature of the male when eventually it occupies +a territory—the impulse of self-assertiveness. +Therefore it seems clear that the different stages +in the process of reproduction mark the appearance +of different conditions, each of which +renders some new impulse susceptible to +stimulation, and that the significance of song +depends upon the stage which happens to +have been reached. Hence when we speak +of song acting as a "warning," we do not +mean that it arouses any sensation of fear; it +is but a stimulus to that part of the inherited +nature of the hearer which predominates at the +moment.</p> + +<p><span class='pagenum'><a name="Page_154" id="Page_154">154</a></span>Are we then justified in the use of such +terms as "warning," "significance," or even +"meaning," when it is but a matter of stimulus +and response? In what does the impulse to +avoid other males consist? There is no reason +to suppose that there is any sensation of fear +in the first stage, and the course of behaviour +demonstrates that there is none in the later +stages. But it is difficult to conceive of an +impulse which has, as its end, the isolation +of the individual from members of its own +sex and kind, without some feeling-tone, the +reverse of pleasurable, entering into the situation; +just as it is difficult to believe that the +female experiences no pleasurable sensation +when she hears the voice of the male that +directs her search. So that the song may be +actually repellent in the one case and attractive +in the other; and it is none the less repellent +when, as in the later stages, it attracts a +neighbouring male, for the attraction is then +of a different order, determined by the presence +of the condition which renders the pugnacious +nature susceptible and leads to attack. In a +sense, therefore, we can speak of "meaning"—though +not perhaps of "significance"—and +of "warning," when we refer to the prospective +value of the behaviour.</p> + +<p>So much for the purpose of "song"; there +still remains the more difficult question—the +question of origin. Let me make clear what +I mean by origin. As we have already seen, +there is infinite diversity in the sexual voice<span class='pagenum'><a name="Page_155" id="Page_155">155</a></span> +of different species; some are harsh and others +monotonous, and some strike the imagination +by their novelty whilst others are melodious; +and to the naturalist each, in its particular +way and in a particular degree, probably makes +some appeal according to the associations that +it arouses. But just why a Marsh-Warbler +is gifted with a voice that is so beautiful and +varied, whilst the Grasshopper-Warbler must +perforce remain content with a monotonous +trill; just why the tail feathers of the Snipe +have developed into an instrument, whilst the +Pied Woodpecker has developed muscles which +enable it to make use of a decayed branch as +an instrument—we know no more than we do +of the nature of the forces which lead the Reed-Warbler +to weave its nest to reeds, or the +caterpillar of the Elephant Hawk Moth to +assume so peculiar an attitude when disturbed. +When therefore I speak of the origin, I do +not refer to the mode of origin of variation; +I take for granted that variations somehow +arise, and I seek to ascertain whether there +is anything in the phenomena which we have +explored which might reasonably be held to +determine the survival of this one in preference +to that.</p> + +<p>When we reflect upon the problem of song +and consider the numerous and diverse forms +in which it is manifested, we are apt to draw +a comparison between the sounds we hear +and those produced by musical instruments, +and hence to conclude that each bird is gifted<span class='pagenum'><a name="Page_156" id="Page_156">156</a></span> +with a special instrument in virtue of which +it produces its characteristic melody. But there +is a very remarkable phenomenon connected +with the singing of birds which shows that this +is really not the case—I mean the phenomenon +of imitation. There are plenty of good imitators +amongst our native species, and the power of +imitation is not the exclusive property of those +which have reached a high degree of vocal +development, nor, for the matter of that, of +song-birds at all. Even the Jay, than which +few birds have a more raucous voice, that +"hoots" like the Wood-Owl, or copies the +sounds produced by the tail feathers of the +Snipe, will occasionally imitate the most +melodious strains of some other species; and +the Red-backed Shrike, whose sexual call is +principally a few harsh notes rapidly repeated, +bursts at times into perfect imitations of the +song of the Swallow, Linnet, or Chaffinch. +Nevertheless it is amongst such typical songsters +as the Warblers that we find the greatest volume +of imitation, and no limit seems to be placed +upon their capacity. The Marsh-Warbler can +utter the call of the Green Woodpecker, or sing +as the Nightingale does, with as much facility +as it sings its own song; and the Blackcap is +well-nigh as proficient in copying the cries +and melodies of surrounding species—and so, +if it were necessary, we might proceed to add +to the list.</p> + +<p>These examples demonstrate that different +songs are not represented by a corresponding<span class='pagenum'><a name="Page_157" id="Page_157">157</a></span> +number of different physiological contrivances; +for if the difference were really attributable to +some structural peculiarity, then the range of +sounds embraced in the call-notes and the sexual +call of any given species, must be the measure +of the capacity of its instrument; and no matter +how great its power of imitation may be, it +follows that it will only be capable of copying +those sounds which fall within that range. +There is plenty of evidence to show that the +power of imitation is almost unlimited, at all +events that it is not confined within such +narrow limits as are here demanded. Hence +it seems clear that the diversity of song is +not to be sought in structure, but in some +innate capacity to play one tune in preference +to another; and if this be so, and if +out of the same instrument, which has been +primarily evolved to further the biological end +of intercommunication, all manner of diverse +sounds can be made to proceed, the problem +of the origin of song is to that extent +simplified.</p> + +<p>We must next inquire into the nature of +song, and endeavour to ascertain whether all +the individuals of a species are alike proficient, +or, failing this, whether there is any quality +which can be observed to be constant under +all conditions. I watch the Reed-Buntings in +a marsh and find that there are three males +occupying adjoining territories. Two of them +are fully mature and their plumage is bright: +that is to say the crown is black, the collar<span class='pagenum'><a name="Page_158" id="Page_158">158</a></span> +and breast are white, the flanks are dull white +spotted with black, and the mantle is reddish-brown. +The third is immature: the crown, +instead of being black, is suffused with brown; +the collar, instead of being white, is mottled with +brown; and the flanks are more heavily streaked +with brown. These three birds take up their +positions in February, and, as is their wont, +sing incessantly each day at daybreak. The +song of the first two is normal, including the +usual number of phrases which flow in no +definite sequence, but are combined and recombined +in different order, and the tone is +pure; that of the third, the immature bird, +is, however, very different; for just as in +comparison its plumage is dull, so the phrases +of its song are limited and reiterated with +great monotony, the tone is impure, and the +whole performance is dull and to our ears +unmusical. I watch them from February to +June, and observe the order in which they are +mated—first a mature male; next, after a short +interval, the immature male; and finally, after +a still longer interval, the remaining bird gets +a mate. As the season advances, still keeping +watch on the development of the plumage +and of the voice of the immature male, I +observe that no very definite change takes +place—that the colours remain dull, that +there is a conspicuous absence in the song of +certain phrases, and that the notes lack purity +of tone.</p> + +<p>If now, instead of Reed-Buntings in a marsh,<span class='pagenum'><a name="Page_159" id="Page_159">159</a></span> +I watch Yellow Buntings on a furze-covered +common, I find that, establishing themselves +early in February, they sing persistently, and +in a few weeks are paired. But what arrests +my attention more particularly is the quality +of the song; for although the voice is unmistakably +the voice of the Yellow Bunting, +yet it is incomplete and lacks the variety of +phrases and musical notation which we customarily +associate with the bird. Nevertheless, as +the season advances, there is a progressive +development in both these directions, and by +the end of March or the beginning of April the +song possesses all those qualities which appeal +to us so forcibly.</p> + +<p>There is one other fact to which attention +must be drawn—the variation in the song of +the same species in different districts. As an +illustration let us take the case of the Chaffinch. +In Worcestershire the bird sings what I imagine +to be a normal song—the notes are clear and +the phrases are distinct and combined in +numerous ways. With the notes fresh in +mind I leave them and go to the west of +Donegal, where I am at once conscious of a +difference; not a subtle difference that perplexes +the mind and is difficult to trace, but +a change so remarkable that one is conscious +of a passing doubt as to whether after all the +voice is the voice of the Chaffinch; the song +is pitched in a lower key, certain phrases are +absent, the notes lack tone and are sometimes +even harsh, and the bird seems wholly in<span class='pagenum'><a name="Page_160" id="Page_160">160</a></span>capable +of reaching the higher notes to which +I am accustomed.</p> + +<p>Now the immature Reed-Bunting, though to +our ears its song is but a poor representation +of that of the adult, gains a mate; the Yellow +Bunting pairs, and the discharge of the sexual +function may even have taken place before its +voice attains what we judge to be its full +development; and there are no grounds for +supposing that the Donegal Chaffinch, with its +less musical notes, has on that account any +the less chance of procreating its kind—facts +which demonstrate that the biological value +of song is neither to be sought in the purity +of tone, nor in the variety and combination of +phrases, nor, indeed, in any of those qualities +by which the human voice gains or loses merit, +and which leave us with no alternative but to +dismiss from our minds all æsthetic considerations +in the attempt to estimate its true +significance.</p> + +<p>What, then, determines its value? Are +there any qualities which, whether the bird is +mature or immature, whether it is untrained +or has acquired fuller expression by practice, +whether it inhabits this district or that, are +alike constant? Well, no matter how great +the variation, no matter how much this voice +falls below or exceeds the standard, judged +from the human standpoint, attained by that, +even we, with our duller perception, have no +difficulty in recognising the species to which +the owner of the voice belongs; in other<span class='pagenum'><a name="Page_161" id="Page_161">161</a></span> +words, the song is always specific, and this is +the most noticeable, as it is the most remarkable, +characteristic.</p> + +<p>There is still, however, another quality to +which I would draw attention—that of loudness. +The sounds produced are on the +whole alike penetrative, and the individuals +of any given district, even though the climate +by affecting their vocal muscles may +have modified the character of the song, are +at no disadvantage in this respect; neither are +the females on the same account the less likely +to hear the undeveloped voice of the immature +male.</p> + +<p>We have then the following considerations: +firstly, there is the widespread and remarkable +phenomenon of imitation, from which we can +infer that the diversity of song is not due to +structural differences but must be sought in +some innate capacity to play one tune in +preference to another; secondly, not all the +individuals of the same species play a similar +tune—we find that there is in certain directions +a noticeable variation which nevertheless does +not seem to affect the question of success or +failure in the attainment of reproduction; in +the third place, in contrast with this variation, +we can observe a striking uniformity in two +important particulars, namely in the specific +character and penetrative power of the song—qualities +which we know are essential for the +purposes of "recognition" and "warning"; and +finally, from the general course of our investi<span class='pagenum'><a name="Page_162" id="Page_162">162</a></span>gation, +we can infer that if a male had no +certain means of advertising its position, the +territory would not be brought into useful +relation in its life. Have we here sufficient +ground on which to construct a theory of +origin; in other words, has the evolution of +song been incidental to, and contributory to, +the evolution of the territory?</p> + +<p>We have all along spoken of the song and +of the call-notes as if they were manifestations +of separate emotional states having their respective +and well-defined spheres of usefulness; +and while, speaking generally, this is a true +statement of the case, there is much evidence +to show that the relationship between them +is nevertheless very close. There are, for +example, quite a number of cases in which a +particular call-note is uttered with unusual +energy during sexual emotion, and is attached +to the song, of which it may be said to form a +part; but a still closer connection can be traced +in many simple melodies which are merely +compositions of social and family calls repeated +many times in succession, and even in some +of the more complex productions there will +be found indications of a similar construction. +And since this is so, since moreover, +in the seasonal vocal development of such a +bird as the Yellow Bunting, we can observe +the gradual elaboration from simple to complex—from +the repetition of single notes to +phrases and from phrases to the complete +melody—we have every reason to suppose that<span class='pagenum'><a name="Page_163" id="Page_163">163</a></span> +it is along these lines that the evolution of +the voice has proceeded.</p> + +<p>In all probability there was a time when +vocal expression was limited to primitive social +and family cries which would be called into play +with special force during times of excitement, +more particularly during the sexual season +which is the period of maximum emotional +excitement. But the excitement would express +itself in all the congenital modes of behaviour +peculiar to the season, and thus the repetition +of these cries would become associated with +combat, with extravagant feats of flight, and +with other forms of motor response. Now the +more emotional individuals would be the more +pugnacious, and all the more likely therefore to +secure territory and so to procreate their kind; +and, being of an excitable disposition, they +would at the same time be the more vociferous. +Hence variations of the hereditary tendency to +vocal expression, even though in themselves +they were not of survival value, would be +fostered and preserved, so long as they were not +harmful, in virtue of their association with +pugnacity. But if, instead of being neutral, +they helped to further the biological end of +combat, the relationship between the voice and +pugnacity would be of a mutually beneficial +kind; and those individuals in which variation +in both directions happened to coincide, would +have a better chance of success in the attainment +of reproduction.</p> + +<p>A territorial system, closely corresponding<span class='pagenum'><a name="Page_164" id="Page_164">164</a></span> +to that which we have discussed, forms part of +the life behaviour of certain mammals, and of +its existence much lower in the scale of life +evidence is not wanting; from which we can +infer that it is not of recent origin, but that +the conditions in the external environment +demanded such a system at a remote period of +avian development. Now even in its incipient +stages the system must have involved a separation +of the sexes, and howsoever slight the +degree of separation may have been in comparison +with that which can be observed to-day, +inasmuch as the power of locomotion was then +less highly developed, mating could only have +proceeded satisfactorily providing that males fit +to breed had some adequate means of disclosing +their positions. Thus there is reason to think +that from the very commencement of the +process variations of emotional disposition +expressed through the voice would have been of +survival value.</p> + +<p>But expressed in what direction, in loudness +and persistency of utterance, these are the +qualities which, I imagine, would have been +more likely to have facilitated the search of the +female? Yet if she were uncertain as to the +owner of the voice, neither loudness nor persistent +repetition would avail much; and as +species multiplied and the competition for the +means of living became increasingly severe, so +the necessity of a territory would have become +intensified, and so, too, with the extension of +range, would the separation of the sexes have<span class='pagenum'><a name="Page_165" id="Page_165">165</a></span> +been an ever-widening one; and as with their +multiplication, irregularities and delays in +mating, arising from the similarity of the calls, +would have increased in frequency, so a distinctive +call, which would have tended to minimise +these risks, would have come to possess +biological value.</p> + +<p>Here we have a theory of origin, but origin +of what? Of certain characteristics of song—nothing +more; and therefore to suppose that it +furnishes a complete explanation, which satisfies +all the requirements of scientific logic, of so +wonderful an intonation as that, for example, of +the Marsh-Warbler, or that no other relationships, +except that of the territory, enter into the +total emotional complex, simplifying here or +elaborating there to meet the exigencies of +diverse circumstances—to suppose this would be +foolish. That there are many relationships +which even to-day are leading to modifications +in important particulars, but which at the +present time are beyond our cognisance, of this +there can be no doubt.</p> + +<p>There is one process by which song may +have attained a fuller development, and which +would account in some measure for the elaboration, +inexplicable merely in terms of "recognition." +It is this: the effect of the sexual call +upon the female cannot well be neutral, it must +be either pleasurable or the reverse—it must, that +is to say, be accompanied by some suggestiveness, +and by suggestion I mean the arousing of some +emotion akin to that of the male; and if there<span class='pagenum'><a name="Page_166" id="Page_166">166</a></span> +are degrees of suggestiveness, which well there +may be, some males will mate sooner than others +and some will remain mateless—this is the +theory of sexual selection. The question to be +decided here is whether the biological emphasis +is on loudness, or specific distinctness, or pitch, +or modulation, or the manner in which the +phrases are combined—that is, on some qualities +in preference to others—or whether the emphasis +is on the whole. We have already seen, and it +is well known, that there is much variation in +the voices of different individuals of the same +species, and thus the first condition of the theory +is fulfilled. Now the conditions which lead to +variation are threefold—immaturity, seasonal +sexual development, and isolation. Of the +three, the variation in the case of the immature +bird is the most instructive; the tone is not so +pure, the combination of phrases is incomplete, +and elaboration is imperfect, and yet, notwithstanding +all these imperfections, we can observe +that the bird pairs as readily as does the adult. +But even if we lacked this demonstrative +evidence, we should still be justified in assuming +that such must be the case, for we know from +experience in the preservation of game, where +there is no surer way of reducing the stock than +by leaving too high a percentage of old cocks, +that for the young bird to be at any disadvantage +in competition with the adult is detrimental, if +not disastrous, to the species. So that while +there is plenty of evidence of variation in those +particular qualities which appeal to our æsthetic<span class='pagenum'><a name="Page_167" id="Page_167">167</a></span> +faculties, there is at the same time evidence +which demonstrates that such variations exercise +no influence on the course of mating; and +inasmuch as it is difficult to conceive of +any voice departing more from the normal +type in these particular qualities than the +immature does from the adult, if there be +degrees of suggestive influence, we must seek +it in some other direction. There remain the +two other characteristics which we found to +be constant under all circumstances, namely, +loudness and specific distinctness; and if, in +addition to serving the purpose of disclosing +the positions of the males, they serve to +evoke some emotion in the female, which +helps to further the biological end of mating, +so much the more reason is there for their +survival.</p> + +<p>There can be no question that this ingenious +and attractive theory, if it were true in its +special application to song, would immensely +simplify interpretation, and moreover that +preferential mating would contribute not a little +to the success of the whole territorial system. +No one can deny the strength of the argument: +that the sexual instinct, like all other instincts, +must require a stimulus of an appropriate kind; +that the effect of the sexual call upon the +female cannot be neutral; and hence the probability +that stimulation varies too; no one, I +say, can question the strength of this evidence, +and, one might add, of the evidence derived +from the analogy of the human voice. But<span class='pagenum'><a name="Page_168" id="Page_168">168</a></span> +when we have said this, we have said all; +and our acceptance of the hypothesis, so far +as song is concerned, must remain provisional +so long as the evidence remains but secondary +evidence.</p> +<hr /> +<p><span class='pagenum'><a name="Page_169" id="Page_169">169</a></span></p> +<h3>CHAPTER V</h3> + +<h4>THE RELATION OF THE TERRITORY TO THE +SYSTEM OF REPRODUCTION</h4> + + +<p>In the first two chapters I tried to show that +the inherited nature of the male leads it to +remain in a definite place at a definite season +and to become intolerant of the approach of +members of its own sex, and that a result is +thus attained which the word "territory" in +some measure describes. But the use of this +word is nevertheless open to criticism, for it +denotes a human end upon which the highest +faculties have been brought to bear, and consequently +we have to be on our guard lest our +conception of the "territory" should tend to +soar upwards into regions which require a level +of mental development not attained by the +bird. It is necessary to bear this in mind +now we have come to consider the meaning +of the territory, or rather the position that it +occupies in the whole scheme of reproduction.</p> + +<p>Relationship to a territory within the interrelated +whole of a bird's life serves more than +one purpose, and not always the same purpose +in the case of every species. We have only<span class='pagenum'><a name="Page_170" id="Page_170">170</a></span> +to glance at the life-histories of divergent forms +to see that the territory has been gradually adjusted +to suit their respective needs—limited in +size here, expanded there, to meet new conditions +as they arose. Now some may think that the +theory would be more likely to be true if the +territory had but one purpose to fulfil, and +that one the same for every species; and they +may see nothing but weakness in the multiplication +of ways in which I shall suggest it may +be serviceable. But such an objection, if it +were raised, would arise from a mistaken conception, +a conception which, instead of starting +with a relationship and working up to the +"territory," sees in the "territory" something +of the bird's own selection and thence works +back to its origin. Holding the view that it +is nothing but a term in a complex relationship +which has gradually become interwoven in +the history of the individual, I see no reason +why the fact of its serving a double or a treble +purpose should not be a stronger argument +for its survival. I now propose to examine +the various ways in which the territory may +have been of use in furthering the life of the +individual, and the circumstances in the inorganic +world which have helped to determine its +survival.</p> + +<p>The purpose that it serves depends largely +upon the conditions in the external environment—the +climate, the supply of food, the +supply of breeding-stations, and the presence +of enemies. Hence its purpose varies with<span class='pagenum'><a name="Page_171" id="Page_171">171</a></span> +varying conditions of existence. But before +we proceed to examine the particular ways +in which it has been modified to suit the needs +of particular classes of species, and the reason +for such modifications, we must inquire whether +there is not some way in which it has been +serviceable alike to every species, or at least +to a large majority of them.</p> + +<p>Success in the attainment of reproduction +depends upon the successful discharge of the +sexual function; and the discharge of the sexual +function depends primarily upon an individual +of one sex coming into contact with one of the +opposite sex at the appropriate season and +when its appropriate organic condition arises. +Now the power of locomotion is so highly +developed in birds that it may seem unreasonable +to suppose that males and females would +have any difficulty in meeting when their +inherited nature required that they should do +so, still less reasonable to suggest that this +power might even act as a hindrance to +successful mating. Nevertheless, if we try to +picture to ourselves the conditions which would +obtain if the movements of both sexes were in +no wise controlled, and mating were solely +dependent upon fortuitous gatherings, we shall +come, I fancy, to no other conclusion than that +much loss of valuable time and needless waste +of energy would often be incurred in the search, +and that many an individual would fail to +breed just because its wanderings took it into +districts in which, at the time, there happened<span class='pagenum'><a name="Page_172" id="Page_172">172</a></span> +to be too many of this sex or too few of that. +And as the power of locomotion increased +and the distribution of the sexes became more +and more irregular, so the opportunity would +be afforded for the development of any variation +which would have tended to facilitate the +process of pairing, and by so doing have conferred +upon the individuals possessing it, some +slight advantage over their fellows.</p> + +<p>What would have been the most likely +direction for variation to have taken? Any +restriction upon the freedom of movement of +both sexes would only have added to the +difficulties of mating; but if restriction had +been imposed upon one sex, whilst the other +had been left free to wander, some order would +have been introduced into the process. That +the territory serves to restrict the movements +of the males and to distribute them uniformly +throughout all suitable localities, there can be +no question; and since the instinctive behaviour +in relation to it is timed to appear at a very +early stage in the seasonal sexual process, the +males are in a position to receive mates before +the impulse to mate begins to assert itself +in the female.</p> + +<p>We will take the Ruff as an example. +According to Mr. Edmund Selous, pairing, in +this species, is promiscuous—the Ruffs are +polygamous, the Reeves polyandrous. Suppose, +then, that upon this island of some few +miles in circumference, whereon his investigations +were made, the movements of neither Ruff<span class='pagenum'><a name="Page_173" id="Page_173">173</a></span> +nor Reeve were subject to control, that the +birds wandered in all directions, and that the +union of the sexes were fortuitous, would the +result have been satisfactory? We must +remember that the Reeve requires more than +one Ruff to satisfy her sexual instinct; we must +also bear in mind the possibility that the +functioning of her instinct may be subject to +some periodicity, and we ask whether, under +these circumstances, accidental gatherings would +meet all the requirements of the situation. +Now, manifestly, she must be in a position to +find males when her appropriate organic condition +arises. But in the absence of any system in the +distribution of the sexes, how could delay be +avoided, or how could a uniform discharge of +the sexual function be assured? There is, +however, a system. In the first place, there +are the assembly grounds to which the birds +repair season after season; and then, on the +assembly grounds, there are the territories, +represented, as Mr. Selous tells us, by depressions +where the grass by long use has been worn +away, and each depression is owned by one +particular Ruff. The assembly grounds have +the effect of splitting up and scattering the +birds, and the number of Ruffs at any one particular +meeting place is limited by the territories; +with the result that Ruffs fit to breed are evenly +distributed and always to be found in certain +definite places, and the Reeves know by experience +where to find them.</p> + +<p>The advantage of this territorial system is<span class='pagenum'><a name="Page_174" id="Page_174">174</a></span> +therefore apparent. Instead of this district +being overcrowded and that one deserted; +instead of there being too many of one sex +here and too few of the other sex there; instead +of a high percentage of individuals failing to +procreate their kind, just because circumstances +over which they have no control prevent their +discovering one another at the appropriate time—each +sex has its allotted part to play, each +district has its allotted number of inhabitants, +and the waste of energy and the loss of time +incurred in the process of mating is reduced to +a minimum.</p> + +<p>Let us return again to the question of +fortuitous mating, and consider the position of +a male and female that have discovered one +another by accident and have paired; what will +be the subsequent course of their behaviour? +We are assuming, of course, that a territory +forms no part of their life-history. If the +discharge of the sexual function takes place +immediately and the ovaries of the female are +in an advanced state of seasonal development, +the construction of the nest will proceed without +delay—and the nest will answer the same +purpose as the territory in so far as it serves to +restrict the movements of the birds and tends to +make them remain in, or return to, its vicinity; +but if not, there will be an interval during which +both sexes will continue to wander as before, +guided only by the scarcity or abundance of +food. In the first case, there will be the +attraction of the nest to prevent any untimely<span class='pagenum'><a name="Page_175" id="Page_175">175</a></span> +separation; in the second, there will be nothing +in the external environment to induce them to +remain in any particular spot. Now if we turn +to any common species and observe the sequence +of events in the life of different pairs, we shall +find that pairing is seldom followed by an +immediate attempt to build; that an interval +of inactivity is the rule rather than the exception, +and that this interval varies in different +species, in different individuals, and in different +seasons. Our imaginary male and female will +therefore be faced with considerable difficulty; +for with nothing in the external environment to +attract them and with no restriction imposed +upon the direction or extent of their flight, their +union will continue to be, as it began by being, +fortuitous. Next, let us consider their position +were a disposition to establish a territory to +form part of the inherited nature of the male. +Each one will then be free to seek food when +and where it wills and to associate with other +individuals without the risk of permanent +separation from its mate; and, no matter how +long an interval may elapse between mating and +nest-building, each one will be in a position to +find the other when the appropriate moment for +doing so arrives. Hence, while preserving +freedom of movement for each individual, the +territory will render their future, as a pair, +secure.</p> + +<p>No doubt the course of behaviour, as we +observe it to-day in the lives of many species, is +the outcome of, rather than the condition which<span class='pagenum'><a name="Page_176" id="Page_176">176</a></span> +has led to, the evolution of the territory. Thus, +in many cases, we find that early mating is the +rule rather than the exception; we find that the +sexes frequently separate to seek their food, and +fly away temporarily in different directions; +and, under exceptional climatic conditions, we +find that they even revert to their winter routine +and form flocks; only, however, to return to +their territories, as pairs, under more congenial +conditions. Yellow Buntings, for example, pair +comparatively early in the season—some in the +latter part of February, others in March, and +others again in April; and some build their +nests in April, others in May. There is a gorse-covered +common which I have in mind, a +favourite breeding resort of this species. +Between this common and the surrounding +country, the birds constantly pass to and fro. +If you watch a particular male you will observe +that it sings for a while in its territory, that it +then rises in the air and disappears from view, +and finally that it returns to the tree, bush, or +mound which constitutes its headquarters, where +it again sings. Meanwhile the female, with +which there is every reason to believe that this +male has paired, behaves similarly; she, too, flies +to the surrounding country and in time returns +with equal certainty. Sometimes male and +female accompany one another—that is, they +leave simultaneously and likewise return; at +other times, though they depart together, the +male returns alone; or the male may disappear +in one direction whilst the female does so in<span class='pagenum'><a name="Page_177" id="Page_177">177</a></span> +another—and, on the whole, there is a sameness +in the direction of flight taken by the same pairs +on different occasions. An interval of nearly +two months may thus elapse between mating +and nest-building, during which the sexes are +not only often apart but often separated by a +considerable distance.</p> + +<p>What does this species gain by the +individuals belonging to it mating so early in +the season? If the appropriate condition which +leads the females to seek males were to arise +in each individual at a late date, the first stage +in the process—mating—would not be completed +before the second—the discharge of the +sexual function—were due to begin. Thus, +instead of having ample time, the females +would have but a short period in which to +discover males; and this in some cases might +lead to delay, in others to failure, and in +others again to needlessly severe competition, +entailing physical exhaustion at a critical +moment in their lives. Hence those females +in which the appropriate organic condition +developed early in the season would not only +be more likely to find males, but would be +in a position to rear more broods than those +in which it developed late; and they would +have a better chance of leaving offspring, +which, in their turn, would reproduce the +peculiarities of their parents. Moreover, within +certain limitations, the more these successful +females varied in the date of their development, +the less severe would be the competition, and<span class='pagenum'><a name="Page_178" id="Page_178">178</a></span> +the more uniformly successful would the mating +of all the individuals in a given district tend +to become. But all of this renders an interval +of sexual inactivity unavoidable; an interval +which must constitute a danger unless there +were something in the external environment +to prevent the male and female from drifting +apart. Inasmuch, then, as the occupation of +a territory serves to remove all possibility of +permanent separation, I suggest that its evolution +has afforded the condition under which +this beneficial procedure has developed—free +to mate when they will, free to seek food +where they will, free to pursue their normal +routine of existence, and to meet all exigencies +as they arise in their ordinary daily life—whilst +free to do this, their future, as a pair, +is nevertheless secure.</p> + +<p>Thus far we have considered the territory +in its relation to the discharge of the sexual +function. In many of the lower forms of life, +the success or the failure of reproduction, so +far as the individual is concerned, may be said +to end with the completion of the sexual act—the +female has but to deposit her eggs in a +suitable environment and then her work is done, +because in due course and under normal conditions +of temperature the young hatch out, and +from the first are able to fend for themselves. +And so, when we come to consider the question +of reproduction in the higher forms of life, we +are apt to focus attention too much upon the +sexual function and too little upon the con<span class='pagenum'><a name="Page_179" id="Page_179">179</a></span>tributory +factors, the failure of any one of +which would mean failure of the whole. For +a bird, success in the attainment of reproduction +does not merely imply the successful discharge +of the sexual function; much more is demanded; +it must find somewhere to build its nest and +to lay its eggs, it must shield its young from +extremes of temperature and protect them from +enemies, and it must be in a position to supply +them with food at regular intervals. And, +consequently, every situation is not equally +favourable for rearing young; there must be a +plentiful supply of food of the right kind in +the immediate vicinity of the nest, and it must +be in greatest abundance just at the moment +when it is most urgently needed—that is to +say, during the first few weeks after the birth +of the young. Success, therefore, depends upon +manifold relationships which centre in the +station, and these relationships vary in intensity +with the conditions of existence.</p> + +<p>First, then, let us examine the problem from +the point of view of the food-supply. There +are many species whose success in rearing +offspring is largely dependent upon the rapidity +with which they can obtain food; and it makes +but little difference which species we choose +out of many—Finch, Bunting, Warbler, or +Chat. I shall choose the Buntings, as their +life-history in broad outline conforms to the +general type, and, moreover, their behaviour +is fresh in my mind. The young are born in a +very helpless state; they are without covering<span class='pagenum'><a name="Page_180" id="Page_180">180</a></span> +—fragile organisms, ill-fitted, one would think, to +withstand extremes of temperature, and wholly +incapable of protecting themselves from enemies +of any description. For the first three days +after they are hatched the female spends much +of her time in brooding them, and, when she +is thus occupied, the male sometimes brings +food to her, which she proceeds to distribute +or swallows. But all the young cannot be fed, +neither are they ready to be fed, at the same +moment; and the parents have besides to find +food for themselves, and the nest has to be +cleaned—all of which necessitates the young +being exposed to the elements at frequent +intervals. Now it is impossible to observe the +instinctive routine of the parents, when the +young need attention, without being impressed +with the conative aspect of their behaviour. +Why, we ask, are the movements of the female +so brisk; why does she seek food and clean +the nest so hurriedly; why, if her instinctive +routine is interrupted, do her actions and her +attitude betray such bewilderment? I take it +that the only answer we can give to these +questions is that the part of her inherited +nature which predominates just at this particular +time is to brood. But why is brooding +of such importance? Partly to maintain the +young at the proper temperature, and thereby +to induce sleep—and sleep for offspring newly +hatched is as important as food—and partly to +protect them from the risk of exposure to +extremes of temperature. This latter danger<span class='pagenum'><a name="Page_181" id="Page_181">181</a></span> +is no imaginary one. Examine a young bird +that has recently left the egg; observe its +nakedness; and consider what it has to withstand—a +temperature that may rise to 70° F. +or may fall to 40° F., the tropical rain of a +thunderstorm or the persistent drizzle of many +hours' duration, the scorching effect of a +summer sun or the chilling effect of a cold +north-easterly wind, and, constantly, the sudden +change of temperature each time that the +parent leaves the nest. One marvels that +it ever does survive; one marvels at the +evolution of a constitution sufficiently elastic +to withstand such changes. But, however +much the constitution may give us cause to +wonder, it is clear that much depends upon +the parents. A slight inefficiency of the +instinctive response which the presence of the +young evokes, a little slowness in searching +for food or sluggishness in returning to the +nest, might lead to exposure and prove fatal. +And, however much is demanded of the parents, +it is clear that much also depends upon the +relationships in the external environment; for +no matter how sensitive or how well attuned +the instinctive response of the parent may be, +it will avail but little in the presence of +unfavourable conditions in the environment.</p> + +<p>Everything turns upon the question of the +effect of exposure. And in order to ascertain +how far extremes of temperature are injurious, +I removed the nests of various species containing +newly hatched young, and, placing them<span class='pagenum'><a name="Page_182" id="Page_182">182</a></span> +in surroundings that afforded the customary +amount of protection from the elements, I made +a note of the temperature and the atmospheric +conditions and then observed the condition of +the young at frequent intervals. Details of +these experiments will be found at the end of +the chapter.</p> + +<p>The experiments with the Blackbirds and +the Whitethroats gave the most interesting +results. Both broods of each species were +respectively of much the same age, yet one +brood of Blackbirds survived for five, and the +other only for two and a half hours, and one +brood of Whitethroats lived for twelve hours +whilst the other succumbed in a little over an +hour. This difference is rather remarkable; +and it seems clear that the power of resistance +of the young diminishes rapidly when the +temperature falls below 52° F. It must be +borne in mind, however, that the conditions +under which the experiments were made were, +on the whole, favourable—the weather was dry, +the temperature was not unusually low, nor was +the wind exceptionally strong or cold; and even +in those cases in which the young succumbed so +rapidly, the atmospheric conditions could by no +means be regarded as abnormal.</p> + +<p>What, then, would happen in an unusually +wet or cold breeding season? For how long +would the young then survive? In the spring +and early summer of the year 1916, I was +fortunate in observing the effect of exposure +under natural but inclement conditions. I<span class='pagenum'><a name="Page_183" id="Page_183">183</a></span> +happened to be watching the Yellow Buntings +on Hartlebury Common—200 acres of Upper +Soft Red Sandstone, profusely overgrown with +cross-leaved heath (<i>Erica tetralix</i>), ling (<i>Calluna +vulgaris</i>), and furze (<i>Ulex</i>)—in one corner of +which eight males had established adjoining +territories covering some fifteen acres of ground. +The males obtained mates towards the end of +March or at the beginning of April; nests were +built in the middle of May, and the successful +pairs hatched out their young in June. On +the 10th June the weather became exceptionally +cold, and during the next ten days the temperature +fell at times to 40° F. during the daytime. +Slight frosts were registered at night in the +district, and the young bracken, which covered +the Common in places, had the appearance of +having been scorched and eventually withered +away. At the coldest period of this cold spell +the young were hatched in two of the nests—in +the first one on the 10th June, and in the second +a day or so later; and on the morning of the 10th +June, having found a suitable position near the +first nest, I began to watch the movements of +the parents, with the intention of keeping some +record of their behaviour each day so long as +the young needed attention. An hour passed +without their appearing, and on examining the +young I found that they were cold, feeble, and +unresponsive, but the female presently arrived +and went to the nest. Later in the day the +young were lively and responded freely when +the nest was approached, but nevertheless I was<span class='pagenum'><a name="Page_184" id="Page_184">184</a></span> +impressed with the length of time during which +the parents were absent; for, judging by the +experience of previous experiment, there seemed +to be every likelihood of their losing their +offspring in such abnormally cold weather, +unless they brooded them more persistently. +On the 11th June at 5.50 <span class="smcaplc">A.M.</span> neither parent was +to be seen and the young could scarcely be made +to respond; but shortly afterwards both male +and female appeared, and, after remaining a +few minutes, again disappeared without even +approaching the nest. At 6.45 <span class="smcaplc">A.M.</span> no attempt +had been made to brood and the young were +then so feeble that they were scarcely able to +open their mouths, and at 6 <span class="smcaplc">P.M.</span> one was still +alive but the remaining three were dead. Yet +the parents returned and the female went to the +nest; and, from a distance of a few feet, I +watched her brooding the living and the dead. +At 5.45 <span class="smcaplc">A.M.</span> the following day the remaining +young bird had succumbed, the temperature +then being 49° F.</p> + +<p>At the second nest, I was unable to watch +the behaviour of the parents so closely. On the +15th June the nest contained three young from +three to four days old, and during the morning +of that and the succeeding day nothing unusual +occurred, with the exception that the period of +exposure seemed, as in the former case, to be +too long. On the 17th June at 3.10 <span class="smcaplc">A.M.</span> the +young had collapsed and were stiff, but the +parents were in their territory and anxious +apparently to attend to their brood. At 9.15<span class='pagenum'><a name="Page_185" id="Page_185">185</a></span> +<span class="smcaplc">A.M.</span> only two of the young were left in the +nest, and though I searched amongst the undergrowth +and in the gorse bush in which the nest +was placed, no trace of the third bird was to be +found. Of the two remaining young, one was +alive and responsive but the other was dead, +and though the female attended assiduously to +the sole surviving offspring, yet it too had +succumbed by the following morning.</p> + +<p>In a third territory, there was a nest containing +four eggs. These eggs were due to +hatch at much the same time as those in the +two nests just referred to, but they failed to do +so, and an examination showed that they contained +well developed but dead chicks.</p> + +<p>To what can the death of the young and of +the chicks in the eggs be attributed? Not to +any failure in the instinctive response of the +females, for they fed their young, they brooded +them, they even brooded the dead as well as the +living, and probably did all that racial preparation +had fitted them to do. Yet the fact that +the young in the second nest were lifeless and +exposed at 3 <span class="smcaplc">A.M.</span> seems to betoken absence on +the part of the parents during the night, and +may be interpreted as a failure of the parental +instinctive response. Let us return for a +moment to the experiments. These showed, it +will be remembered, that a rise or fall in the +temperature of but a few degrees was sufficient +to make an astonishing difference in the length +of time that the young were able to survive +without their parents; that when the tempera<span class='pagenum'><a name="Page_186" id="Page_186">186</a></span>ture +reached 58° F. the bodies of the young +retained their warmth, and that under such +conditions even a night's exposure had little, if +any, effect; so that even supposing that the +parents were absent during the night, the death +of the young cannot be said to have been due to +a failure of the parental instinct, because under +normal conditions—and under such has their +instinctive routine been evolved—their absence +would not have prejudiced the existence of the +offspring. I attribute the collapse of the young +solely to the exceptional cold that prevailed at +just the most critical time, and I base this +conclusion partly on the experience gained from +experiment, but mainly on their condition +observed at different intervals; for during +exposure they collapsed rapidly, their flesh +became cold and their movements sluggish, +their response grew weak, and gradually they +became more and more feeble until they could +scarcely close their bills after the mandibles had +been forced asunder. Yet, even after having +reached so acute a stage of collapse, the warmth +from the body of the brooding bird was +sufficient to restore them temporarily; once +more they would become lively and responsive, +only, however, to revert to the previous condition +soon after the parent had again abandoned +them. Doubtless their power of resistance +grew less and less during each successive period +of exposure.</p> + +<p>If the nestling Bunting is to be freed from +the risk of exposure, it is evident that there<span class='pagenum'><a name="Page_187" id="Page_187">187</a></span> +must be, in the vicinity of the nest, an adequate +supply of food upon which the parents can draw +liberally. Hence those pairs that exercise +dominion over the few acres surrounding the +nest, and are thus able to obtain food rapidly, +will stand a better chance of rearing their +offspring than others which have no certain +supply to draw upon—and this, I believe, is one +of the biological ends for which the territory has +been evolved. But it must not be supposed +that each pair finds, or even attempts to find, +the whole of the food within its territory, or +that it is necessary for the theory that it should +do so; all that is required is that such overcrowding +as might lead to prolonged absence on +the part of the parents and inordinate exposure +of the young shall be avoided. So that the +problem has to be considered not merely from +the point of view of the individual, but from the +larger point of view of all the pairs inhabiting +a given area.</p> + +<p>Now there were eight pairs of Yellow +Buntings occupying the one corner of Hartlebury +Common, and their territories in the +aggregate covered some fifteen acres. The +birds obtained part of their food-supply amongst +the gorse and in some young scattered oak-trees, +and part in an adjoining coppice and on +the surrounding arable land. But they were +not the sole occupants of this corner of +the Common; other insectivorous species had +territories there also—amongst which were +Whitethroats, Grasshopper-Warblers, Willow-Warblers,<span class='pagenum'><a name="Page_188" id="Page_188">188</a></span> +Whinchats, Stonechats, Meadow-Pipits, +Tree-Pipits, and Skylarks. Suppose +then that there had been sixteen pairs of Yellow +Buntings instead of eight; that there had been +other pairs, which assuredly there were, inhabiting +the locality; that they had also resorted, +which assuredly they did, to the coppice and +arable ground for the purpose of securing food; +and that their numbers had also been increased +in a similar ratio—would a supply of food for +all have been forthcoming with the necessary +regularity and promptitude? Well, the parents +might have had to travel a little farther; but +even if they had been compelled to do so, their +absence would only have been prolonged by so +many minutes the more, and under normal +conditions what harmful result to the offspring +could possibly have followed? The question for +us, however, is not what might have occurred +under normal conditions, but whether the life +behaviour is so adjusted as to meet the exigencies +of diverse, and in this case of abnormal, circumstances. +Now the capacity of the young to +resist exposure diminishes very rapidly when the +temperature falls below the normal—the danger +zone seems to be reached at approximately +52° F., and the length of time during which they +survive then becomes astonishingly short—and +moreover the fall in the temperature would tend +to decrease the supply of insect life upon which +they depend, so that if the size of the territories +had been reduced by one half, and the parents +in consequence had been compelled to seek their<span class='pagenum'><a name="Page_189" id="Page_189">189</a></span> +food at a greater distance, can it be doubted +that the cumulative effect of even a few minutes +of additional exposure would have been detrimental, +if not disastrous, to the offspring?</p> + +<p>We speak, however, of the parents extending +their journeys a little farther in this direction or +a little farther in that, as though they could do +so with impunity except in so far as it affected +themselves, or their offspring, or the other +Yellow Buntings inhabiting that particular area. +But, most certainly, any extension would have +meant so much encroachment upon the available +means of support of other members of the +species inhabiting adjoining areas, whose young +in turn would have been liable to have been +affected; and, with even greater certainty, the +Whitethroats, the Stonechats, the Tree-Pipits, +and the Willow-Warblers that had also +established themselves in that one corner of +the Common would have been hard pressed to +find sufficient food with sufficient rapidity.</p> + +<p>Let me give another illustration of a somewhat +different kind. Lapwings, as we saw in +the previous chapters, establish territories and +guard them from intrusion with scrupulous care. +The young are able to leave the nest soon after +they are hatched, and consequently the parents +are not necessarily obliged to bring food <i>to</i> +them—they can, if they so choose, lead them <i>to</i> +the food. Whether each pair limits its search +for food to its territory, I do not know. But +even supposing that all ownership of territory +were to lapse directly the young were hatched,<span class='pagenum'><a name="Page_190" id="Page_190">190</a></span> +that the boundaries were to cease to exist, and +that the birds were free to wander at will +without fear of molestation, the end for which +the territory had been evolved would none the +less have been obtained; for inasmuch as the +parents are accompanied by their young, it +matters not in what part of the meadow they +seek their food; all that matters is that the +number of families shall not exceed the available +supply of food. So far, then, as the Lapwing is +concerned, the territory fulfils its purpose when +once it limits the number of males, since, by +doing so, it limits the number of families and +prevents undue pressure upon the means of +support.</p> + +<p>Nevertheless, there are many birds that +seem to rely entirely upon the territory to +supply them with all that is necessary. Each +Warbler seeks its food within the precincts +of its own particular domain, and, except in +occasional instances, neither resorts to neutral +ground nor makes excursions into the locality +immediately surrounding the territory, as does +the Bunting. Probably it would be disastrous +if it attempted to do so, for since its young +at birth are so delicate and so susceptible to +changes of temperature, it cannot afford to +be absent from them for long. Of the two +experiments made with young Whitethroats, +one was made under favourable and the other +under unfavourable conditions. In this latter +case the temperature was 50° F., and the young, +it may be remembered, only survived for a<span class='pagenum'><a name="Page_191" id="Page_191">191</a></span> +little over one hour. Now exposure at that +temperature is evidently dangerous, but it +would be still more dangerous if the weather +were wet instead of dry, and the temperature +46° F. instead of 50° F.; and it is, I imagine, +on this account that the impulse to brood is +so strongly implanted in the female. No +sooner, it seems, does she depart than she +returns with a small quantity of food which +she hurriedly distributes and immediately settles +down to brood; and if forcibly prevented from +returning, her attitude betrays symptoms of +what, humanly speaking, we should term great +distress. If, then, the conditions in the external +environment were such as would make it +difficult for the female to obtain food rapidly, +what advantage would she derive from so +strongly developed an impulse? Might it +not be a disadvantage? Might it not mean +that she would abandon the search too readily +and be content to return with an insufficient +supply, and might not that be as injurious to +the young as prolonged exposure? Manifestly +the impulse to brood could only have developed +strength in so far as it fitted in with all the +other factors that make for survival; and the +principal factor in the external environment +seems to be the territory. How could the +young have been freed from the risk of +exposure if the impulse to brood had not +been so strongly implanted in the parent? +How could the impulse to brood have been +free to develop if a supply of food had not<span class='pagenum'><a name="Page_192" id="Page_192">192</a></span> +been first insured? How could the supply +of food have been insured if numbers of the +same species had been allowed to breed in +close proximity?</p> + +<p class="tb">From the foregoing facts it is clear that the +young of many species are at birth susceptible +to cold and unable to withstand prolonged +exposure. The parents must therefore be in +a position to obtain food rapidly, and consequently +it is important that there should be +an ample supply in the vicinity of the nest. +This end the territory certainly serves to +promote; it roughly insures that the bird +population of a given area is in proportion to +the available means of subsistence, and it +thus reduces the risk of prolonged exposure +to which the young are always liable.</p> + + +<p>This leads on to a consideration of those +cases in which the question of securing food +is subordinate to the question of securing a +station suitable for reproduction.</p> + +<p>I take the Guillemot as an example. In +principle its behaviour is similar to that of the +Bunting; the male repairs to a definite place, +isolates itself, and becomes pugnacious. But +the Guillemot is generally surrounded by other +Guillemots, and the birds are often so densely +packed along the ledges that there is scarcely +standing room, so it seems, for all of them. +Nevertheless the isolation of the individual +is, in a sense, just as complete as that of the +individual Bunting, for each one is just as<span class='pagenum'><a name="Page_193" id="Page_193">193</a></span> +vigilant in resisting intrusion upon its few +square feet as the Bunting is in guarding its +many square yards, so that the evidence seems +to show that that part of the inherited nature +which is the basis of the territory is much +the same in both species. What we have then +to consider is, What is the biological value to +the Guillemot of an inherited nature which, +for the Bunting, has utility in relation to the +supply of food for the young? Up to a point, +the act of securing a territory has like value +for each respective species, whether the area +occupied be large or small—that is to say, it +enables the one sex to discover the other with +reasonable promptitude.</p> + +<p>For the greater part of the year, Guillemots +live at sea; singly, in twos or threes, or in +small parties, they move upon the face of the +waters, extending their wanderings far away +from land, out into the broad ocean, where +for weeks together they face the gales and +heavy seas of the Atlantic. But in due course +and in response to internal organic changes, +they return, like the Warbler, to their breeding +grounds—rocky headlands or islands appropriately +situated and affording the appropriate +rock formation. During all these months of +wandering, the majority seem to ignore the +land, to pass away from it altogether, and to +spread themselves over the surface of the ocean +regardless of mainland or island. Some useful +observations, which throw some light on the +distance that Guillemots are accustomed to<span class='pagenum'><a name="Page_194" id="Page_194">194</a></span> +wander from land, were made by Lieut. B. R. +Stewart during a number of voyages between +various ports in Great Britain and Ireland and +ports in North America, principally New York +and Quebec. Thus, on the 24th March, large +numbers were seen in lat. 55° N., long. 24° W., +five hundred miles approximately from land, +though on the following day—four hundred +miles off Tory Island—they were not so plentiful. +Again, on the 1st October, in lat. 53° N., long. +27° W., seven hundred miles or so from land, one +bird was seen, whilst on the following day, in +lat. 52° N., long. 21° W., a single individual +was washed on board by the heavy seas and +seemed little the worse for the adventure. +Within two hundred miles of the west coast +of Ireland, he found them plentiful on various +occasions. From this it is clear that the circumstances +under which the bird lives for many +months in succession must impose a considerable +strain upon its constitution; and how it is able +to withstand the buffeting of wind and water, +to secure its food, and to endure, is a mystery. +It is important, therefore, that the young bird +should be properly nourished and protected +from anything that might harm its constitution, +and important, too, that the parents should be +freed from any undue strain during the course +of reproduction.</p> + +<p>The conditions which the breeding station +has to fulfil are threefold: in the first place, +it must be in proximity to the food-supply; +secondly, it must provide the necessary shelter<span class='pagenum'><a name="Page_195" id="Page_195">195</a></span> +for the egg and for the helpless offspring; +and, in the third place, it must be so situated +that the young can reach the water in safety. +We will examine these conditions one by +one.</p> + +<p>The proximity to the food-supply is a +consideration of some importance. The life +of the Guillemot during the winter is a +strenuous one; we know that large numbers +succumb in stormy weather, and we can infer +that slight constitutional defects might make +all the difference between failure and success; +and, therefore, the less severely the constitution +of the parent is taxed during reproduction, +and the more securely the constitution of the +offspring is built up, the greater prospect +will both have of resisting the hardships of the +winter successfully. Much, then, will depend +upon the distance the parents have to travel +in order to obtain food. The farther the +breeding station is removed from the feeding +ground the greater the physical strain which +will be imposed upon the birds, and the greater +the chance will there be of the offspring being +improperly nourished. Now the food consists +of small fish, largely of sand-eels, which are +secured in deep water, and the abundance of +which varies, possibly according to the nature +of the currents. Hence cliffs which are situated +away from the water, or from which the water +recedes at low tide, or which are surrounded +by an area of shallow water, and are thus not in +proximity to the feeding ground, even though<span class='pagenum'><a name="Page_196" id="Page_196">196</a></span> +they may fulfil the second and third condition, +will not answer the requirements of a breeding +station.</p> + +<p>Of no less importance is the type of rock-formation. +Not every formation affords the +necessary ledges upon which the egg can be +deposited with safety—the face of the cliff may +be too smooth, or too jagged, or the shelves +may run at too acute an angle. Many of the +large assemblages of Guillemots in the British +Islands are found where the rock is quartzite, +mica-schist, limestone, or chalk. The reason of +this is that such rocks are weathered along the +planes of stratification, of jointing, of cleavage, +or of foliation—the strata being probably of +unequal durability—with the result that innumerable +shelves, ledges, and caverns, which +are taken advantage of by the birds, form a +network over the face of the cliff. But only +those ledges can be made use of which are +placed at a considerable height above the water, +because, when the cliff faces the open sea, the +lower ones are liable to be washed in stormy +weather by the incoming swell and thus become +untenable. There is a small cove in the midst +of the most precipitous part of the breeding +station at Horn Head, wherein the shingly +shore shelves rapidly to the Atlantic and faces +to the west. Here, towards the end of July, +young Kittiwake Gulls can sometimes be found +washed up on the beach—some living, but in +every stage of exhaustion, others dead, and in +every stage of decomposition; here is the young<span class='pagenum'><a name="Page_197" id="Page_197">197</a></span> +bird, recently caught by the swell and thrown +upon the shore, lying side by side with the +remains of others that had previously succumbed +to starvation—on every side evidence of the +devastation wrought by the Atlantic. May not +some of this destruction have been brought +about by the nests having been placed upon +the lower ledges within reach of an exceptionally +heavy sea? Hence much depends upon the +nature of the rock-formation, and many a +mighty precipice, even though it may fulfil +the first and third condition, is nevertheless +valueless as a breeding station.</p> + +<p>Finally, the young bird must occupy a ledge +from which it can reach the water in safety. +There is much difference of opinion as to the +manner in which it leaves the ledge, but all +agree that it does so before it is capable of +sustained flight. If, then, the face of the cliffs +were made up of a series of broken precipices, or +if the rocks at the base projected out into the +water, or if detached rocks abounded in the +waters beneath, the mortality amongst the chicks +would no doubt be considerable.</p> + +<p>The coast-line of Co. Donegal will illustrate +the foregoing remarks. On the southern and +western side of the Slieve League promontory +there is no real Guillemot station; only on the +northern side—the quartzite in the vicinity of +Tormore—are the birds to be found in large +numbers. Northwards from here, a wild and +rugged coast is passed over before other stations +are reached—at the eastern end of Tory Island<span class='pagenum'><a name="Page_198" id="Page_198">198</a></span> +and on Horn Head; and beyond this, to the +east, there are none, not even on the old rocks +that form the promontory of Inishowen. Why, +we ask, do countless numbers crowd the ledges +of Horn Head, whilst they are absent from the +precipices of Slieve League; why, too, are they +absent from the granite cliffs of Owey? The +reason is not far to seek. Either the face of +the cliff is made up of a series of broken +precipices, or the face of the precipices is +too smooth, or the otherwise suitable ledges +are situated too near the water, or the water +recedes from the base of the cliff at low tide. +Many miles of rock-bound coast are thus useless +for the purpose of reproduction.</p> + +<p>Now when we bear in mind how large an +expanse of coast is formed of blown sand or of +rocks of low altitude, and how many miles of +cliff fail to supply the three essential conditions +that we have been considering, we can see +that suitable breeding stations must be limited +both in number and extent. From a wide +expanse of ocean hosts of individuals are therefore +obliged to converge at certain definite +points; and hence, each recurring season, there +must arise a competition for positions at the +station, just as there is competition between +individual Buntings for positions in the marsh. +And the ability to obtain a position upon a +suitable ledge involves, in the first place, +an impulse to search for it; in the second +place, an impulse to dwell in it; and in the +third place, an impulse to resist intrusion<span class='pagenum'><a name="Page_199" id="Page_199">199</a></span> +upon it. It would be useless for an individual +to be pugnacious if it had no fixed abode; +equally useless for it to establish itself on a +particular ledge if it had no power to defend it—all +of which implies an inherited nature similar +to that of the Bunting. But the proximate end +to which the competition is directed is not alike +in the case of both species. In the case of the +Guillemot it has reference solely to the piece of +rock whereon the egg is laid; in the case of the +Bunting to a piece of ground capable of furnishing +an adequate supply of food for the young; +and the reason for the difference is this, that +there is always an abundance of food in the +water beneath the cliff, but breeding stations are +scarce, whereas there is always an abundance of +situations in the marsh in which the Bunting +can place its nest, but the supply of food varies +and at times can only be obtained with +difficulty.</p> + +<p>If then the Guillemot were to behave after +the manner of the Bunting and assign to itself a +portion of the face of the cliff, or if it were only +to occupy a few ledges, or an even lesser area—a +single ledge—what would be the result? That +it would attain to reproduction is beyond +question; that the egg would be safely deposited +there can be no manner of doubt; neither is +there any reason to suppose that the offspring +would not be successfully reared. But, indirectly, +its behaviour would affect the Guillemot +race. For if it be true, as the crowded ledges +certainly seem to show, that there is a dearth of<span class='pagenum'><a name="Page_200" id="Page_200">200</a></span> +suitable breeding ground, no greater calamity +could befall the species than that some members +should exercise dominion over too large an area +of the habitable part of the cliff and thus +prevent others from breeding. Under such +conditions the race could not endure, since in +this, as in every case, its survival must depend +upon a close correspondence between the +behaviour of the individual and the circumstances +in the external environment.</p> + +<p>Scarcity of suitable cliffs is the principal +reason of the ledges being so closely packed +with Guillemots, just as it accounts for this +part of the precipice being crowded with Kittiwake +Gulls, that part with Herring-Gulls, and +that part again with Razorbills and Puffins. +Yet each individual preserves its few square +feet of rock or soil from molestation, and the +area each one occupies varies according to the +conditions of existence of the species. Thus +the Herring-Gull occupies a comparatively small +area, although one many times larger than that +of the Guillemot. It requires more space than +the latter, owing to the fact that it not only +builds a nest but rears four instead of a single +offspring, and it can be allowed this, because, +since its young remain in the nest until they are +capable of sustained flight, it can make use of +many miles of cliff from which the tide recedes +at the base, or which have, at their base, +rocks jutting out into the sea; but manifestly +it cannot be allowed so much space as the +Bunting.</p> + +<p><span class='pagenum'><a name="Page_201" id="Page_201">201</a></span>Martins build in close proximity to one +another, owing probably to shortage of accommodation, +and, in their case, the nests have to +be so situated as to be sheltered from the wet. +If water drips upon them for any length of +time, the mud, of which they are composed, +crumbles and large pieces fall away, with the +result that the eggs or the young are precipitated +to the ground. Consequently, not every +house or perpendicular cliff will answer the +purpose of a breeding station. A few pairs +build their nests beneath the eaves close against +the walls of my house, and year after year the +result is much the same; after every downfall +of rain, the water collects into rivulets, trickles +down over the eaves, is absorbed by the mud +and destroys the nests. Thereupon, the birds +set to work and rebuild; but again the nest is +destroyed, and again they rebuild, and so on +throughout the summer, and only on rare +occasions do they succeed in rearing offspring +at the proper season. Similar conditions must +prevail in many situations; but, clearly, the +more binding and plastic the building material, +the longer the nest will withstand the action of +the dripping water and the greater chance will +there be of the young being reared in safety. +Observe, therefore, how far-reaching an effect so +small a detail as the nature of the mud can have +upon the status of the species in any given +locality. Where the conditions are favourable, +there the birds must congregate to breed, and, +like the Guillemot, if each individual exercised<span class='pagenum'><a name="Page_202" id="Page_202">202</a></span> +dominion over too large an area, the species as +a whole would suffer.</p> + +<p>In all these examples, the fact of different +individuals being in such close proximity may +afford some protection from enemies both as +regards the egg and the offspring, and in so far +as there is a mutual advantage such assemblages +may be spoken of as communities. A community, +however, in the true sense of the word, +is a collection of individuals brought together, +not primarily as a result of shortage of breeding +ground, but in consequence of advantages of +communal ownership over individual ownership. +A rookery is an example of a true community. +Neither shortage of nesting accommodation nor +scarcity of food can account for Rooks assembling +together to breed; for if the different +pairs which go to make up the rookery were to +scatter throughout the surrounding neighbourhood, +they would, as a rule, find plenty of trees +in which to build their nests, and plenty of food.</p> + +<p>How, then, can the theory apply to a species +that breeds under such conditions? What part +can the territory play in furthering the life of +the individual when large numbers of nests are +built closely together in the same tree? There +is much evidence to show that mutual protection +is a necessary condition of the Rook's +existence; many cases are on record of rookeries +being destroyed by Carrion-Crows, Hooded +Crows, and Ravens. For instance, Mr. Ward +Fowler records a case in which a pair of Crows +attacked a small rookery, ransacked the nests,<span class='pagenum'><a name="Page_203" id="Page_203">203</a></span> +and destroyed the eggs, with the result that not +a single pair of Rooks was left in the settlement. +Each Rook must therefore secure a position +within the precincts of the community if it is to +have a chance of success in the attainment of +reproduction. But every locality cannot supply +sufficient trees of the right kind, appropriately +situated and in suitable relation to the food +supply, in which numbers of nests can be built +in close proximity; so that if more than one +community were to attempt to establish itself in +a limited area, the supply of food or the supply +of trees might become a pressing problem. +Each community must therefore be prepared +to defend its own interests, and each must be +regarded as one unit and the area occupied +as one territory within which are included a +number of lesser territories. The individual +may fail to establish itself within a community, +but, even if it succeeds, the community may fail +to establish the rights of communal ownership; +hence it has to face a twofold possibility of +failure, and if it lacked the inherited nature +which leads the Guillemot to secure a position +upon the ledge, or the Bunting to obtain a +position in the marsh, the chances are that it +would fail in the attainment of reproduction.</p> + +<p>The question now arises as to how it comes +about that the area occupied by each individual +conforms in broad outline to that which has +proved beneficial for the welfare of the species +as a whole. We shall find that up to a point +the answer is a simple one. No one could study<span class='pagenum'><a name="Page_204" id="Page_204">204</a></span> +the behaviour of animals without observing the +important part that habit plays in the life of the +individual; an action performed to-day is liable +to be repeated to-morrow and the following day +until it becomes ingrained in the life of the +individual. This must not be taken to mean, +however, that a particular action has to be +performed for many days in succession before +it becomes definitely fixed; if only it is repeated +a number of times, even within the space of +a few hours, it will acquire sufficient strength +for its continuance; but continued repetition +gives increased fixity, and, as time goes by, it +becomes increasingly difficult for the creature to +make a change unless the character of the +situation necessitates readjustment.</p> + +<p>For example, when the organic condition +which leads to nest-building becomes active, +the bird tentatively collects some of the +necessary material in its bill, flies round with +it, and then drops it. After a while it collects +some more, and this time leaves it perhaps in +a bush. Later on it makes another attempt, +and, meeting with a situation which calls forth +the appropriate response, it thereupon lays the +foundation of the structure. We will assume +that the nest is placed in the midst of a tangled +bush. Well, the bird lays the first strands of +the foundation and then goes in search of more +material. The next time it approaches the nest +from the opposite side of the bush, and presently +it finds yet a third entrance. But each entrance +is not made use of in turn: one is employed<span class='pagenum'><a name="Page_205" id="Page_205">205</a></span> +more frequently than the other two, and in the +course of time becomes the sole highway to and +from the nest. Suppose now that, when the +young are hatched, I cut away the foliage from +the bush on the opposite side from that on +which the bird customarily enters, and by so +doing leave the nest exposed, what is the result? +The female arrives with food, threads her way +through the bush, and, when beside the nest, +pauses as if aware that some change had taken +place, and then flies away through the new +opening. In a short time she returns, flits from +twig to twig on the outskirts of the bush, +and comes upon the new opening—there she +hesitates. But though the nest is in full view +and within a few inches of her perch, and though +the young stretch out their necks, yet so strong +is the former habit that she is compelled to +return to the opposite side and approach the +nest by the usual circuitous route before she +distributes the food amongst her offspring.</p> + +<p>Let us see how far this law of habit +formation may have been effective in defining +the extent of the area occupied. When a male +Warbler arrives at its destination in the spring +it seeks out a suitable environment, and, having +found a place unoccupied by any other male, +settles in it and remains there—its behaviour +up to this point being determined by racial +preparation. After the fatigue of the journey +its movements are at first sluggish; hunger, +however, asserts itself and a search is made for +food; wandering away from the position in<span class='pagenum'><a name="Page_206" id="Page_206">206</a></span> +which it first settled and which acts as a headquarters, +it hunts through certain trees here or +certain bushes there and returns, and presently +it wanders away again, perhaps in another +direction, but, as before, works its way back +again to the headquarters. The journeys thus +radiate outwards from the headquarters, and +according to the success with which the bird +meets, so, probably, it happens that some trees +are searched more often than others and certain +directions are taken more frequently than others, +and by constant repetition a routine is established +which limits the direction and scope of its +wanderings.</p> + +<p>But in the case of the Guillemot the +conditions of existence are reversed: food can +be had in abundance but suitable breeding +stations are scarce. The few square feet of +ledge correspond to the tree or clump of bushes +which acts as a headquarters for the Warbler, +and the occupation of them is determined, as +it is in the case of the Warbler, by racial +preparation. Since, however, the ledge is only +made use of for the immediate purpose of +incubation and is in no way affected by +questions relating to food, there is no occasion +for the bird to wander along the ledge nor to +encroach upon those adjoining. Hunger stimulates +the Warbler to search the surrounding +trees, and so to extend its area; but hunger +takes the Guillemot down to the water, and +hence the area which it primarily occupied +remains unmodified.</p> + +<p><span class='pagenum'><a name="Page_207" id="Page_207">207</a></span>To sum up: the territory is useful in various +ways, but not necessarily in the same way +for every species. Reproduction would always +have remained fortuitous, and the number of +individuals that attained to it would seldom +have reached the possible maximum unless some +provision had been included in its system for +insuring that the males and females could meet +at the proper moment and afterwards remain in +touch with one another, and that the number of +pairs inhabiting a given area did not exceed the +available means of support. I have tried to +show that the inclusion of a disposition to secure +a territory tends to remove these difficulties. +In the first place, the disposition which leads to +its occupation comes into functional activity (in +the male) early in the season; and so, by the +time that the appropriate pairing condition +arises in the females, the process of acquiring +territories is well advanced, and the males being +regularly distributed, each in its respective +position, are readily found by their prospective +mates. The behaviour of each sex is thus +adjusted to further the end of mutual discovery. +Next, after mating has taken place, the position +occupied by the male acts as a headquarters to +which the birds can always repair, and becomes +a bond of union which is serviceable in that it +prevents any possibility of their drifting apart. +And in the third place, the males become +pugnacious and in this way secure for themselves +areas which vary in size according to the +conditions of existence of the species, so that<span class='pagenum'><a name="Page_208" id="Page_208">208</a></span> +there is no possibility of too many congregating +in this locality, and all the less likelihood of too +few finding their way to that; and hence, on the +average, different pairs are distributed throughout +all suitable localities. Furthermore, owing +to the fact of their having a headquarters, the +male and female are allowed a freedom of +movement which otherwise they would only +possess when the construction of the nest had +actually begun; they can seek their food +independently, and, even though paired, they +can if necessary continue their winter routine +without risk of separation. This means that the +organic condition which leads to pairing, is free +to develop in the female earlier than would be +the case if there were nothing in the external +environment to attract the pair to a particular +spot; and the longer the period over which the +process of pairing can be spread, the greater +chance will females have of discovering mates, +the less severe will the competition tend to +become, and, consequently, the smaller the +percentage of individuals that fail to obtain +suitable partners.</p> + +<p>In these ways the territory has been serviceable +alike to a number of species. But much +as the questions of mutual discovery and regular +distribution may have influenced the course of +its development, there can, I think, be little +doubt that, on the one hand, the supply of +the necessary accommodation for rearing offspring, +and on the other, the necessity for an +adequate supply of food in close proximity to<span class='pagenum'><a name="Page_209" id="Page_209">209</a></span> +the nest, have been the main determining factors, +and have led to a wide divergence in its function. +At the one extreme the function is to insure +a plentiful supply of food for the young; at the +other, to insure a station suitable for rearing +offspring. I took the Bunting and the Guillemot +as types of the two extremes. The young of +the former species are born in a very helpless +state. They are susceptible to cold and unable +to withstand prolonged exposure, and therefore +it is essential that there should be an ample +supply of food, upon which the parents can +draw liberally, in the vicinity of the nest. But +the nest is placed in a variety of situations, and +accommodation in this respect may be said to +be unlimited. The young of the latter species +are not so susceptible to exposure, and moreover +there is always an abundance of food in the +waters beneath the cliff; but ledges of rock, +upon which the egg can be securely deposited +and the young successfully reared, are limited +both in number and extent. The position then +is as follows: there are situations in plenty in +which hosts of Buntings can build their nests +but the supply of food is a difficulty, and if the +respective areas of different individuals were +insufficient to supply them with the necessary +food with the necessary rapidity, they would +run the risk of losing their offspring and the +species would not endure; on the other hand, +cliffs upon which the Guillemot can rear its +young are limited, but the supply of food +presents no difficulty, and consequently the<span class='pagenum'><a name="Page_210" id="Page_210">210</a></span> +smaller the area over which each individual +exercises dominion, the greater the number +that will attain to reproduction and the greater +prospect the species will have of survival. The +emphasis in the one case lies on the fact that +the area occupied must be sufficiently large; +on the other, on its being just sufficient and +no more to accommodate the egg. Hence +the difference in the function at the opposite +extremes is brought about, not by modifications +of the instinctive behaviour which leads to the +establishment and defence of the territory, but +solely by modifications in the size of the area +occupied, in accordance with the conditions +prevailing in the external environment. No +doubt, if we had the life-histories of a sufficient +number of species worked out, we should find +that the gradations were complete from the +one extreme to the other. We are justified +in thinking that this must be so because in +many directions we can not only observe +differences in the size of the area occupied, but +can recognise a close correspondence between +those differences and the conditions of life of +the species. Thus the Herring-Gull occupies +a comparatively small area, though one which +is many times larger than that of the Guillemot. +It requires more space because it not only builds +a nest but rears four instead of a single offspring, +and it can be allowed more space because the +young remain in the nest until they are capable +of sustained flight, and consequently it can +make use of many miles of cliff from which the<span class='pagenum'><a name="Page_211" id="Page_211">211</a></span> +tide recedes at the base, and which on this +account are denied to the Guillemot, but +manifestly it cannot be allowed so much space +as the Bunting, for then comparatively few +individuals would attain to reproduction.</p> + +<p>Again, the Reed-Warbler inhabits swamps +overgrown with the common reed, and in such +places insect life is abundant just at the +time when the young are hatched. But these +swamps cover a comparatively small acreage in +the breeding range of the bird, and if each pair +were to attempt to establish dominion over an +area equal, let us say, to that of the Willow-Warbler, +the species would have but a poor +chance in the struggle for existence. So that, +in a case of this description, the supply of food +and the comparative scarcity of breeding stations +have been factors of like importance in the +evolution of the territory.</p> + +<p>Finally we were led to inquire as to how +it comes about that the extent of the area +occupied by each individual is adapted to the +circumstances in which the individual finds +itself; and we came to the conclusion that the +movements of the bird, subsequent to the +initial act of establishing itself in a position, +are regulated and defined by the law of habit +formation. For example, the Warbler, in +response to its inherited nature, takes up a +position in an appropriate situation. It then +proceeds to search for food; it makes short +journeys first in this direction and then in +that; it repeats these journeys, and gradually<span class='pagenum'><a name="Page_212" id="Page_212">212</a></span> +forms a habit which compels it to remain +within more or less well-defined boundaries. +But the actual distance that it traverses on +the occasion of its first attempt must be determined +by the relative abundance or scarcity +of the particular kind of insect life which it +requires. So that, although habit defines and +in some measure helps to determine the +boundaries of the territory, it is clear that in +the last resort they must depend upon the +nature of the conditions in the external +environment.</p> + +<p>We have, then, the congenital basis which +leads to the occupation of a position, and to +the enmity shown by the owner of the position +towards other individuals; and this congenital +basis is found alike in many widely divergent +forms, living under equally widely divergent conditions; +we have acquired accommodation; and +we have relationships in the organic and inorganic +world—and the outcome of it all is a system +of behaviour which we, who can perceive the +end to which such behaviour is tending, are +justified in speaking of as "a disposition to +secure a territory." In the development of +this system a primary value must be ascribed +to the conditions in the external environment, +for they determine the direction of the variations +of instinctive procedure and of acquired habit +which work towards the same goal—that of +adjustment to the conditions of life.</p> +<hr /> +<p><span class='pagenum'><a name="Page_213" id="Page_213">213</a></span></p> +<h3>NOTE</h3> + + +<p class="tb2">The following are the experiments referred to on +page 181:—</p> + + +<p class="tb2">On the 14th May 1915, a nest of Blackbirds approximately +four days old was removed at 6.45 <span class="smcaplc">A.M.</span> The +temperature was considerably below the normal, and snow +lay on all the high ground in the neighbourhood. In a +short time the birds collapsed, and at 9.15 <span class="smcaplc">A.M.</span> were dead. +On the 29th May, at 6 <span class="smcaplc">A.M.</span>, a second nest was removed, +containing young of approximately the same age, and +although the conditions were more normal, the temperature +being 50° F., the birds collapsed at 8 <span class="smcaplc">A.M.</span>, and an +hour later one of the brood showed little signs of life. +The wind, however, then changed to the west, and the +temperature rose one degree, with the result that they +were still living at 11 <span class="smcap">A.M</span>. A further experiment was +made with Song-Thrushes on the 5th June. The wind was +in the south and the temperature 63° F. The young, +approximately four days old, were removed at 7.25 <span class="smcaplc">A.M.</span>, +but as they showed no signs of collapse at 1 <span class="smcaplc">P.M.</span> I replaced +the nest in the original site.</p> + + +<p class="tb2">On the 30th May, a nest of Whitethroats three days +old was removed at 7.15 <span class="smcaplc">A.M.</span> The wind was northerly +and the weather fine, but the temperature low—50° F. +At 8.15 <span class="smcaplc">A.M.</span> the birds showed no sign of life. A second +experiment with this species was made on the 10th June +under more favourable circumstances, for although the +sky was overcast and the wind northerly, the temperature +was 59° F. In this case the young survived from 6.55 <span class="smcaplc">A.M.</span> +to 7 <span class="smcaplc">P.M.</span></p> + + +<p class="tb2">On the 27th May 1915, a nest of Hedge-Sparrows +hatched the previous day was removed at 7 <span class="smcaplc">A.M.</span> The +temperature was below the normal, being 49° F. At<span class='pagenum'><a name="Page_214" id="Page_214">214</a></span> +8 <span class="smcaplc">A.M.</span> the young were cold and in a state of collapse, but +they survived nevertheless until 3.20 <span class="smcaplc">P.M.</span></p> + + +<p class="tb2">On the 7th June 1915, a nest of young Skylarks three +days old was removed at 7.15 <span class="smcaplc">A.M.</span> The temperature was +62° F., and the birds survived until 4 <span class="smcaplc">A.M.</span> the next day.</p> + + +<p class="tb2">On the 6th June 1916, a nest of Linnets just hatched +was removed at 6.47 <span class="smcaplc">A.M.</span> The temperature was 51° F. +At 7.50 <span class="smcaplc">A.M.</span> the birds were cold and in a state of collapse, +and only survived until 8.50 <span class="smcaplc">A.M.</span></p> +<hr /> +<p><span class='pagenum'><a name="Page_215" id="Page_215">215</a></span></p> +<h3>CHAPTER VI</h3> + +<h4>THE WARFARE BETWEEN DIFFERENT SPECIES +AND ITS RELATION TO THE TERRITORY</h4> + + +<p>We have now considered the various ways in +which the territory is useful in furthering the +life of the individual. We have seen that, in +some cases, there is competition for stations +where the egg or eggs can be deposited and +incubated in safety; that, in others, there is +competition for stations capable of furnishing +an adequate supply of food for the young; +and that the establishment of "territories" +not only renders the attainment of reproduction +for the individual secure, but serves so to +regulate the distribution of pairs that the +maximum number can be accommodated in +the minimum area. This being so, the question +arises as to whether competition for territory +is strictly limited to individuals of the same +species, or whether it may not occur also +between different kinds of birds, providing +always that similar conditions of existence +are required. First of all I shall relate a +number of facts which will serve to show the +nature and extent of the warfare, and I shall<span class='pagenum'><a name="Page_216" id="Page_216">216</a></span> +then give the reasons which lead me to believe +that the fighting not only bears some relation +to the "territory," but that it is an important +factor in contributing to the attainment of that +which for biological interpretation is the end +for which the whole territorial system has been +evolved.</p> + +<p>Those who have studied wild life on one of +the rocky headlands, which are so numerous +round our coasts, will probably be familiar with +the rivalry that exists between the Raven and +certain birds of prey. Where the Raven finds +shelter for its nest, there, too, the Peregrine +has its eyrie—and so it happens that these two +species are continually at war. Now the warfare +occurs not only during the season of +reproduction but continues throughout the +greater part of the year, and can even be +observed in the late summer or early autumn—the +period when we should expect to find the +instinct least susceptible to appropriate stimulation. +But it is of a more determined kind +early in the spring, and it is then that we often +witness those remarkable exhibitions of flight, +the skill of which excites our admiration. The +Falcon rises above the Raven, stoops at it, and +when it seems no longer possible for a collision +to be avoided, or, one would imagine, for the +Raven to escape destruction, the Raven skilfully +turns upon its back and momentarily faces its +opponent, and the Falcon with equal skill +changes its course, passing upwards and away. +The attack, however, is soon repeated, and<span class='pagenum'><a name="Page_217" id="Page_217">217</a></span> +though no collision may actually take place, yet +the fact that the Raven, when it turns to face +its adversary, is obliged to drop the stick which +it carries, is not only an indication of the +character of the struggle, but it shows that a +definite end is gained—that the efforts of the +Raven to build in that particular locality are +hampered. But the Falcon is not the only +enemy that the Raven has to face; Buzzards +are just as intolerant of the presence of Ravens +in their neighbourhood as the Ravens are of +them, and consequently there is incessant +quarrelling wherever the same locality is +inhabited. As a rule, the fighting occurs whilst +the birds are on the wing; the Buzzard rises to +a considerable height, and, closing its wings, +stoops at the Raven below, and when within a +short distance of its adversary, swerves upwards +and gains a position from which it can again +attack. The Buzzard, however, is by no means +always the aggressor; I have watched one so +persistently harassed by a Raven that at length +it left the rock upon which it was resting and +disappeared from view, still followed by its rival. +Thus it seems as if they were evenly matched, +and, when they occupy the same locality, it is +interesting to notice how the initiative passes +from the one to the other according to the +position occupied by the birds in their respective +territories.</p> + +<div class="figcenter" style="width: 500px;"><a name="f255" id="f255"></a><img src="images/fig255.jpg" width="500" height="450" alt="Peregrine Falcon +attacking a Raven" title="Peregrine Falcon attacking a Raven." /></div> + +<p>That there is constant warfare between the +Green Woodpecker and the Starling is well +known, the purpose of the Starling being to<span class='pagenum'><a name="Page_218" id="Page_218">218</a></span> +gain possession of the hole which the Woodpecker +with much skill has drilled for itself. +As far as my experience goes, the Starling is +always the aggressor, and there is only too good +reason to fear that, in the course of time, the +Green Woodpecker will disappear as a result of +the greater fertility and tenacity of its enemy. +The Martin suffers a similar kind of persecution +from the House-Sparrow, and here again there +is reason to believe that the greater virility of +the Sparrow will hasten the extinction of its +rival. In cases of this description the purpose of +the fighting is clear, and one can understand +why such divergent species should be hostile to +one another; yet others, equally remote in the +scale of nature, are hostile when no such +ostensible reason can be assigned for their +hostility. Few birds are more pugnacious than +the Moor-Hen, and the determined manner +in which different individuals fight with one +another is notorious. But the intolerance it +displays towards other species is no less remarkable, +and its pugnacious instinct seems to be +peculiarly susceptible to stimulation by different +individuals belonging to widely divergent forms. +At one moment a Lapwing may be attacked, +at another a Thrush or a Starling, harmless +strangers that have approached the pool to +drink; even a Water-Rail, as it threads its way +through the rushes, may fail to escape detection; +and, which is still more curious, a covey +of Partridges will evoke response if they +approach the pool too closely.</p> + +<p><span class='pagenum'><a name="Page_219" id="Page_219">219</a></span>Here is a curious instance of apparent waste +of energy. A pair of Magpies built their nest +in an ilex tree. Early one morning there was +a commotion in the tree, much flapping of +wings and a medley of sounds which told of +large birds engaged in a struggle—the Magpies +were attacking a pair of Wood-Pigeons. There +was no question as to the genuineness of the +struggle, nor any doubt as to the proximate end +for which the Magpies were striving, for their +efforts continued so long as the Wood-Pigeons +remained in the tree, and only ceased when they +had succeeded in driving them away.</p> + +<p>Turning next to species which are less +distantly related, we find that instances of +intolerance are more numerous and that a wider +range of species is involved. The hostility that +the Lapwing displays towards the Snipe calls +for special remark. It often happens that the +marshes or water meadows, that are such +favourite haunts of the Lapwing, are also +resorted to by Snipe for the purpose of securing +food, or it may be even for the purpose of +reproduction. In such places both species are +often abundant; the meadow is divided up into +Lapwings' territories, and early in the season the +Snipe wander over it in small parties, singly, or +in pairs. Now, if it were only on isolated +occasions that the Lapwing paid heed to the +Snipe, one would not perhaps attach any +peculiar significance to the fact; but the +pugnacious instinct of the bird responds to the +presence of this intruder almost as freely as it<span class='pagenum'><a name="Page_220" id="Page_220">220</a></span> +does to that of another Lapwing. Again and +again, day after day, the Snipe are attacked and +driven off in a manner which would be fittingly +described as persistent persecution, for the Snipe +has neither the physical capacity nor apparently +any instinctive tendency to retaliate. Thus a +Lapwing may come suddenly upon a small +party of Snipe hidden from view in a dyke +where they are probing the ground for food; +the Snipe immediately rise and fly away and +there is momentary confusion as the Lapwing +darts first at this one, then at that; or, espying +a Snipe at rest at the opposite end of its +territory, it will first of all run rapidly towards +it, and then fly after it, as, with twisting flight, +it darts hither and thither a few feet above the +ground; or again, it will attack and rapidly +pursue solitary individuals as they skim across +its territory and attempt to settle. Is this +intolerance merely an exuberant expression of +an instinct which is serviceable in another +direction? The behaviour of the Lapwing +scarcely justifies such a conclusion, for all its +actions denote a striving towards some end +which we can describe, and it seems to gain +satisfaction only when the ejection of the +intruder has been accomplished.</p> + +<p>Many of the Warblers display irritation +when approached by other birds which we +should scarcely expect would arouse their +hostility. The Hedge-Sparrow, for example, is +frequently regarded with suspicion, and it is +by no means unusual to see it attacked by so<span class='pagenum'><a name="Page_221" id="Page_221">221</a></span> +small a bird as the Chiffchaff. The Wood-Warbler +is also pugnacious, and will even attack +a pair of Chaffinches. Between the Tit family +and some of the smaller Warblers there are +constant exhibitions of hostility; even the Great +Tit is liable to be driven away, but the Blue +Tit is especially marked out for persecution, +though doubtless it is well able to hold its own.</p> + +<p>The following incident will show how real is +the antagonism between these two families. +A Chiffchaff occupied the corner of a small +osier bed, and was particularly aggressive +towards other closely-related forms in its +immediate neighbourhood. On two mornings +in succession ten Blue Tits invaded its ground, +passing from end to end of it as they wended +their way from tree to tree in search of food. +Their presence evoked the usual hostile response, +yet, withal, aroused the fear of the Chiffchaff, +which, at times, appeared to be swayed by +conflicting impulses. Now, in attempting to +interpret the nature of the instinct which was +evoked, one has to be guided, in a case of this +description, by the similarity of the response to +that which can be observed on other occasions +and in other situations when the intention of +the bird is clear. And on this occasion the +Chiffchaff betrayed all the symptoms which +normally precede an attack; it spread its tail, +quivered its wings, uttered its high-pitched note +rapidly, hopped from twig to twig, or flew +restlessly from tree to tree, and seemed to be +prevented from attacking only by the number<span class='pagenum'><a name="Page_222" id="Page_222">222</a></span> +of its opponents. This, indeed, was shown by +its subsequent behaviour, for whenever a Tit +became temporarily detached from its companions +it hesitated no longer but forthwith +attacked.</p> + +<p>There are other species which are no less +aggressive than the Warblers—the Chats for +example. The Stonechat regards with suspicion +almost any bird of its own size, and will even +pursue a Tree-Pipit if it approaches too closely. +The same is true of the Whinchat, and one +would scarcely expect to find this bird attacking +Buntings as it sometimes does. A Whinchat +that occupied some marshy ground was constantly +at war with a pair of Reed-Buntings; +their territories were adjacent and in some +measure overlapped, and the Whinchat drove +away either sex indiscriminately, and was not +only always the aggressor but seemed to be +master of the situation.</p> + +<p>Coming now to kindred forms, those, that +is to say, which belong to the same family, we +find that, both in intensity and extent, the +warfare far exceeds anything that we have thus +far considered. So frequent, indeed, are acts +of intolerance, and so readily awakened into +activity is the pugnacious nature of the bird, +that the fighting will almost bear comparison +in volume with that which occurs between +individuals of the same species. Between the +Thrush and the Blackbird there are incessant +quarrels early in the year, and the initiative +seems to pass from one to the other according to<span class='pagenum'><a name="Page_223" id="Page_223">223</a></span> +the circumstances in which they are placed. If +the territory of a Thrush is invaded the Thrush +is the aggressor, and, conversely, if that of the +Blackbird is threatened, the Blackbird becomes +the aggressor; and so, when the territories of the +two birds are adjacent or overlap, as frequently +they do, there is constant friction, resulting in +quarrels which attract attention on account of +the noisiness of the birds.</p> + +<p>All the Warblers are exceedingly pugnacious, +the fighting being especially severe between +those that are very closely related. The Blackcap +and the Garden-Warbler are constant rivals, +and the scenes which can be witnessed when +the two meet in competition are interesting +from many points of view. The birds not only +pursue and fight with one another, but their +emotional behaviour reaches a high level of +intensity—excitable outbursts of song are indulged +in, tails are outspread, wings are slowly +flapped, and feathers raised—in fact the attitudes +assumed are similar in all respects to those +which occur during the contests which are so +frequent between the respective individuals of +each species; and it would be difficult to point +to any one item of behaviour which is not +also manifest at one time or another during the +battles between these rivals, and still more +difficult to trace any difference in the intensity +of the excitement. And if we are satisfied that +the fighting in the one case is purposive, so, too, +must we regard it as having some biological +purpose to serve in the other. But the Garden-Warbler<span class='pagenum'><a name="Page_224" id="Page_224">224</a></span> +is not the only bird that acts as a +stimulus to the instinct of the Blackcap; +Whitethroats are often attacked, and the Chiffchaff +is a source of irritation. Even when a +male Blackcap is engaged in incubation, it will +leave its nest on the approach of a Chiffchaff, +and, having driven away the intruder, proceed +to sing excitedly. At other times both male +and female will combine to attack this small +intruder.</p> + +<p>But this does not mean that the Chiffchaff +suffers persecution; it is itself most aggressive, +as is shown by the fact that it will join in the +Blackcap quarrels and attack the combatants +indiscriminately. Its behaviour, however, requires +further consideration, especially as regards +its relations with its nearest of kin—the Willow-Warbler; +for here we have a mutual intolerance +which is somewhat remarkable, and evidence of +it can be found wherever the birds occupy the +same ground. Now it can be observed that the +hostility is not limited merely to occasional acts +of intolerance, but that there is organised +warfare lasting, it may be, for many days in +succession, and that the actions of the birds bear +the stamp of a persistent striving towards some +end. On one occasion the Willow-Warbler +may be the aggressor, on another the Chiffchaff, +and at times it is difficult to say which of +the two is responsible for the quarrel. In size +and in strength they are equal, and the "will to +fight" is as strong in the one as in the other, so +that it is seldom, if ever, possible to point to<span class='pagenum'><a name="Page_225" id="Page_225">225</a></span> +this one as the victor and that one as the +vanquished. Success or failure probably depends +more upon the cumulative effect of many +combats entailing physical exhaustion, than +upon the issue of any one particular battle; and +whilst observation might quite well fail to +distinguish any resultant change in the relative +positions of the birds, or any harmful effect +upon their constitutions, yet the area occupied +by this one might be sufficiently curtailed to +prejudice the welfare of the young, or the +vitality of that one might be seriously impaired—and +we should be none the wiser.</p> + +<p>Neither the Marsh-Warbler nor the Reed-Warbler +will tolerate strangers within the small +space of ground over which they exercise +dominion. Of the two, the Marsh-Warbler is +perhaps the more pugnacious, and will attack +any other Warbler that approaches too closely; +Whitethroats are often pursued and driven +away, and less frequently, Garden-Warblers. +In one case, a male occupied the same ground +as a Sedge-Warbler, and there was a constant +feud between them; a willow-tree formed its +headquarters, and this same tree seemed to be +the headquarters of the Sedge-Warbler, so that +they often met and whenever they did so they +quarrelled. As a rule the Marsh-Warbler was +the aggressor and had the mastery over its +opponent, and when it attacked, it uttered a +peculiar harsh scolding note, raised the feathers +on its back, spread out its wings, and betrayed +the usual symptoms of emotional excitement.</p> + +<p><span class='pagenum'><a name="Page_226" id="Page_226">226</a></span>On the other hand, the Sedge-Warbler is +most aggressive towards other kindred species, +and when a male happens to occupy the same +ground as a Reed-Warbler, there are frequent +battles between them and incessant commotion; +they fly at one another and meet in the air with +an audible clicking of bills, or pursue one +another amongst the reeds, each one uttering +its characteristic scolding note.</p> + +<p>The Tits, as a family, are notoriously +pugnacious. I have seen a pair of Blue Tits +attack a single Long-tailed Tit with great +determination, and not only did they pursue it, +but, flying at it, struck it with considerable +force.</p> + +<p>In giving an account of the domestic +economy of the Carrion-Crow, Mr. Edmund +Selous refers to the hostility between this bird +and the Magpie. "About a week ago," he +says,<a name="FNanchor_6_6" id="FNanchor_6_6"></a><a href="#Footnote_6_6" class="fnanchor">6</a> "I saw a Crow busily engaged in chasing +away several Magpies, not only from three or +four tall slender trees close together, in one of +which it had its nest, but also from various +other trees, not far off, round about. In this +the Crow had a good deal of trouble, as the +Magpies were always returning. After a time +it was joined by another crow, which however +did not take so active a part in the drama, nor +did I see either of the two actually go to the +nest, though I could only explain their action by +supposing it was their own. This morning I +saw the same thing reversed, for a pair of +<span class='pagenum'><a name="Page_227" id="Page_227">227</a></span> +Magpies, with an undoubted nest, kept attacking +a Crow that insisted on settling in one of a row +of trees—also tall and slender—in which it was +placed. Both were equally persevering—the +Crow, though often chased away, always +returning, and settling generally in the last +tree of the row, where he would be left alone +sometimes for a minute or two, but before long +one of the Magpies flew at him, and put him to +flight. The Crow defended itself, but not, it +would seem, very successfully, and in the last +attack upon him, made, with great spirit, in the +air, a large black feather floated to the ground, +which I made no doubt was his. Yet this did +not drive him from the trees, and it was only on +my approaching nearer that he finally left them. +Thus we see that both species look upon the +approach of the other to within a moderate +distance of their nest as an intrusion."</p> + +<p>That the Rook suffers persecution from +the Carrion-Crow is a well-established fact, +and there is reason to believe that it has +another dangerous enemy in the Hooded Crow. +According to the late Mr. Ussher, Choughs will +attack both Hooded Crows and Ravens. "I +once saw," he says, "two Choughs energetically +attacking a pair of Ravens; they shot up into +the air and darted down on the latter, whose +heavy flight made them helpless against their +agile tormentors."</p> + +<p>Birds of prey are often hostile to one another. +The Merlin is exceptionally pugnacious, and its +boldness in attacking intruders is well known.<span class='pagenum'><a name="Page_228" id="Page_228">228</a></span> +When, for example, a Kestrel approaches its +territory, it leaves the tree, bush, or rock upon +which it was resting, utters its characteristic +cry, and soars rapidly upwards; then, rising to +a considerable height, it swoops down upon the +Kestrel, and by alternately stooping at and +chasing its opponent, drives it away from the +immediate neighbourhood.</p> + +<p>What we have, then, to consider is, Do these +battles between different species contribute +towards the attainment of the end for which +the whole territorial system has been evolved?</p> + +<p>Let us take the individual and see whether +we can establish any relation between the +hostility it displays towards members of other +species and its general disposition to secure +a territory. We must remember that a male +can have no knowledge of the prospective +value of its behaviour, nor is it likely that it +has any ulterior purpose in ejecting other males, +beyond the pleasure it derives from satisfying +its impulse to do so. The proximate end of +its behaviour is to attack, nothing more, and +this, of course, it can only do just in so far +as the intruder evokes the appropriate instinct.</p> + +<p>Now the arguments we shall employ will, +on the whole, be similar to those which we +made use of in the second chapter, wherein +we attempted to ascertain the conditions under +which a male becomes intolerant of other +males of its own species, and examined more +especially the claims of the "territory" as +opposed to those of the "female." But here<span class='pagenum'><a name="Page_229" id="Page_229">229</a></span> +we start on firmer ground, because the one +factor which introduced an element of uncertainty—the +female—can be definitely excluded; +at least it seems so to me, for granting even +that her presence is the condition under which +the pugnacious nature of the male is rendered +susceptible to stimulation, it is difficult to see +why a male of a different species should supply +that stimulus, or what biological purpose could +be served by its doing so.</p> + +<p>When dealing with the attitude of a male +towards others of its kind, we attached considerable +significance to the fact that its pugnacious +nature gained or lost susceptibility according +to the position which it happened to occupy. +We found, it will be remembered, that the +same bird that was pugnacious in its own +territory took no further interest in its opponent +when the boundary was passed; and, moreover, +that if it happened to wander into an adjoining +one, it made no real effort to defend itself +when attacked, but returned forthwith to its +own headquarters. It remains to be shown +whether the rivalry between different kinds of +birds is similarly related to the position which +the opponents happen to occupy at the time.</p> + +<p>First, then, there is the general consideration, +namely, that the enmity occurs for the most +part just at the time when the territories are +in process of being established. During autumn +and winter, many birds of more or less close +affinity assemble together in flocks, wherever +the supply of food is abundant, and are then<span class='pagenum'><a name="Page_230" id="Page_230">230</a></span> +not only sociable, but, so there is reason to +believe, are mutually helpful both in discovering +the necessary means of subsistence which are +often none too plentiful, and in affording protection +from enemies, which, on the contrary, +are often numerous. That the different units +of which these flocks are composed should live +on amicable terms is therefore as necessary +for the welfare of the whole community at +this particular season as that the different +individuals of the same species should do so. +But just as the sociable relations, which obtain +between these individuals throughout the winter, +undergo a marked change at the commencement +of the breeding season, so, too, do different +species, which habitually associate together, +suddenly become hostile to one another. This +change is coincident in time with the rise of +the organic condition which leads to the +establishment of territories; and the hostility +continues, though in diminishing degree, +throughout the breeding season, and dies away +the following autumn.</p> + +<p>For example, different Warblers resort to +the elders (<i>Sambucus nigra</i>) in September, and +there pass much time feeding on the fruit which +is then ripe and often abundant. In the same +bush there may be Blackcaps, Garden-Warblers, +Whitethroats, and Lesser Whitethroats, some +preening their feathers, others searching for +the berries, others again, with feathers relaxed, +making feeble attempts to sing. Occasionally +there may be a scuffle, perhaps between a<span class='pagenum'><a name="Page_231" id="Page_231">231</a></span> +Blackcap and a Lesser Whitethroat, or between +a Garden-Warbler and a Blackcap, but it is +of short duration and lacks vigour. Apart, +however, from such temporary disturbances, +there is no real rupture in their relations, and +certainly nothing to lead one to suppose that +the bickerings are determined by the functioning +of any specific instinct. Yet only a few months +previously some of them were constantly at +war, and their quarrels betrayed symptoms of +great persistence; and if we remember how +the observed behaviour of the birds suggests +the fact that they were striving to attain something +definite, we shall understand the nature +and extent of the change, and shall, I fancy, +be in a better position to estimate its biological +worth at its true value.</p> + +<p>We can find many similar examples—flocks +are to be found on arable ground, on the water +meadows, and on the mud-flats; here different +kinds of Thrushes feed on the berries of the +yew, there different kinds of Tits travel together +in parties; hosts of Finches collect in the hollies +to pass the night and Buntings roost together +in the gorse; and, in fact, in whatever direction +we choose to look in the autumn and winter, +we find various birds assembled together and +living on amicable terms. All of this changes +in the spring, and the relationship undergoes +a gradual but noticeable alteration; so much +so that whereas the outstanding feature of bird +life in the winter is sociability, that of the +spring is hostility.<span class='pagenum'><a name="Page_232" id="Page_232">232</a></span></p> + +<p>So much, then, for the seasonal change of +relationship; let us now turn to particular cases +and attempt to trace the condition which +accompanies such change.</p> + +<p>Many migrants in the spring seem to follow +the course of the Severn during their journey +northwards through Worcestershire; and where +the river bends to the north-west at Lincombe +Lock, there they leave it, or, rather, continue +in a north-easterly direction which takes them +across the southern end of Hartlebury Common. +As I have already mentioned, this Common is +overgrown with gorse, heather, and ling, and +scattered here and there are a number of dwarf +oak-trees and small elder-bushes. The situation +is therefore an ideal one for the smaller migrants +to rest for a brief time, and, from the point of +view of the observer, very suitable because it is +open and the movements of the birds can be +traced for some distance. Turtle Doves pass +over at a great height, or skim across a few +feet above the gorse; Redstarts settle for a +few minutes and then disappear; Tree-Pipits, +Whinchats, and Willow-Warblers pass from +tree to tree or flit from bush to bush—and all +in a north-easterly direction. They do not +sing, they are restless, and, judging by their +behaviour, they are anxious to conceal their +presence, not to make it known. Yet we know +that when they reach their destination, as +presently they will, all this will change; that +each of them will employ every means at its +disposal to make itself conspicuous; and that<span class='pagenum'><a name="Page_233" id="Page_233">233</a></span> +each, as far as it is able, will resist intrusion on +the part of other species.</p> + +<p>Now the southern end of the Common is +always inhabited by individuals belonging to +one of these species, or to others of close +affinity; so that wherever these travellers settle +whilst passing across it, the chances are that +they will find the ground occupied—and their +behaviour under such circumstances is no less +interesting than the behaviour of the bird upon +whose ground they are trespassing. We will +take the case of the Whinchat. It arrives from +the south-west, and, flying from bush to bush, +works its way in a north-easterly direction. In +doing so it intrudes upon the territory of +a Stonechat; and the Stonechat, becoming +excited, flies towards it, and it retires for a short +distance in the direction from whence it came. +Here again it is followed and attacked and +again moves on, and then, flying in a circle as if +to avoid the territory which blocked the path, +resumes its former line of flight, though still +followed by the Stonechat, which after continuing +the pursuit for perhaps a quarter of a mile, +suddenly turns in the air and returns to its +headquarters.</p> + +<p>It is difficult to put oneself in the place of +the Stonechat or of the Whinchat. But even +after making due allowance for the danger +inseparable from any attempt to do so, there +remains the unquestionable fact that whereas +the impulse to attack was strong in the one, the +impulse to defend itself was wholly lacking in<span class='pagenum'><a name="Page_234" id="Page_234">234</a></span> +the other. Yet a Whinchat, when it has +established itself, is most pugnacious; it not +only attacks every bird of a similar size that +approaches its position, but its behaviour under +such circumstances bears the impress of unusual +determination; and if we were to take a male +and place it in the position of the Stonechat, we +should find that its nature would change, that +the presence of the Stonechat would evoke a +hostile response, and, conversely, that the +instinct of the Stonechat would not be susceptible +to stimulation. Hence it is clear that the +nature of a bird when on migration is not quite +the same as it is when its destination is reached; +that the positions occupied from time to time +during the journey carry no meaning, or, rather, +are not brought into relation with its life in +quite the same way as is the position which it +finally occupies; and further, it is clear that the +interest it displays in other species undergoes a +somewhat remarkable transformation when at +length its destination is reached.</p> + +<p>This altered nature of the migrant is a fact +of some importance in relation to our present +subject, but it does not stand alone—the same +characteristic is observable in other phases of +bird life. Some of the residents, the Buntings +and the Finches for example, occupy their +breeding ground very early in the year, and it +often happens that the situations which they +select are not capable of supplying them with +food so early in the season, though at a later +date food will be there in abundance; so that<span class='pagenum'><a name="Page_235" id="Page_235">235</a></span> +they are compelled to resort to the surrounding +neighbourhood, and since, even there, the +available supply is sometimes scarce or, if +plentiful, limited to certain areas, they are +constrained from time to time to join together +again in flocks. Thus, for part of the year, +they may be said to lead a double existence; +for just as the Whinchat, that is sociable on +migration, betrays a changed nature when it +reaches its destination, so too does the nature +of these residents change from hour to hour +according to whether they are seeking food or +occupying the breeding ground.</p> + +<p>In the newly-sown fields of grain the birds +frequently find a supply of food. Here Yellow +Buntings, Greenfinches, and Chaffinches collect +from the surrounding neighbourhood. The +majority are somewhere in possession of territories, +and not a few are paired. Between the +territories and the feeding ground a highway is +formed by individuals passing to and fro. +Sometimes both members of the pair leave +together in order to seek food, at other times +they separate and the male may be in his +territory whilst the female is with the flock. +Apart from occasional manifestations of sexual +emotion on the part of a male, there is nothing +to disturb the harmony of the flock nor anything +in the behaviour of the birds which would +lead one to suspect that, when they return, their +nature will change and that they will be no +longer sociable; and, which is still more remarkable, +no matter how great the provocation which<span class='pagenum'><a name="Page_236" id="Page_236">236</a></span> +an individual, when in company with the flock, +may be called upon to endure, its customary +hostile response will fail to be elicited. An +incident which happened in the spring of 1917 +will serve to make this clear. A flock of some +thirty Yellow Buntings, Greenfinches, and +Chaffinches were feeding in one corner of a +field which had recently been sown with barley. +As they sought their food they wandered +outwards into the middle of the field, and in +so doing, passed across the territory of a Skylark. +Whereupon the Skylark became excited, +uttered its call-note rapidly, and rising a few +feet from the ground, attacked those members +of the flock that were nearest, which happened +to be the Yellow Buntings; and so determined +were its onslaughts that the Yellow Buntings +were forced to retire. The Skylark showed no +discrimination as to sex, but attacked both males +and females, and within a few minutes succeeded +in driving away at least two pairs. One would +have expected that the Yellow Buntings would +have made some show of resistance; one would +have thought that the fact of being violently +attacked would have supplied a stimulus +sufficiently strong to evoke a corresponding +hostile response: yet there was no mistaking +the lack of interest that they displayed in the +contest—they made no effort to retaliate but +seemed to accept the situation as unalterable +and left.</p> + +<p>So far we have examined only those cases in +which the pugnacious instinct was stimulated in<span class='pagenum'><a name="Page_237" id="Page_237">237</a></span> +one of the adversaries, and in which consequently +the fighting seldom reached any high degree of +severity. We must now consider some others +in which each of the opponents acts as a +stimulus to the pugnacious instinct of the other. +It is here, of course, that we find the most +violently contested battles, and it is here, too, +that the purpose of the fighting seems clear. +The persecution which the Green Woodpecker +suffers from the Starling is well known. The +purpose of the Starling's behaviour is clear, +namely the possession of the hole occupied +by the Woodpecker. Bird for bird, the Woodpecker +is more than the equal of the Starling, +but persistent endeavour ultimately wins the +day. The Starlings perch close beside the hole, +and, whenever the Woodpecker shows itself, +attack with determination; and not only do +they do so but they are assisted, so there is +reason to believe, by other individuals or pairs +in the attainment of their end, so that no matter +how stoutly the Woodpecker defends itself, in +time it is almost certain to be deprived of its +ownership.</p> + +<p>In like manner different kinds of Woodpeckers +contend with one another for the +possession of a hole, and here the opponents +are more equally matched. I have seen a pair +of Lesser Spotted Woodpeckers endeavouring +to drive away a Great Spotted Woodpecker. +The excitement of all three birds was exceptional. +Each of the Lesser Spotted Woodpeckers kept +swooping in turn at their rival, sometimes in the<span class='pagenum'><a name="Page_238" id="Page_238">238</a></span> +air and sometimes when it was settled on the +topmost branches of a dead tree, and the sounds +produced reminded one of the piping of a flock +of Oyster-Catchers in flight.</p> + +<p>A battle between a pair of Green Woodpeckers +and a Great Spotted Woodpecker is +worth mentioning. It occurred on the 24th of +April. Passing through the middle of a wood, +I noticed a Great Spotted Woodpecker fly out +of a hole in an oak-tree. Shortly afterwards, +a pair of Green Woodpeckers settled near the +hole and then flew to some oak-trees close at +hand, where they were joined by their rival and +signs of hostility were soon apparent. Presently +the Great Spotted Woodpecker returned to the +hole and entered. Both of the Green Woodpeckers +then flew into the tree; and one of +them, settling upon the trunk, climbed up to +the level of the hole and, when it became +aware of the Great Spotted Woodpecker within, +extended its wings fully and proceeded to peck +viciously at its opponent. Whereupon there +was a scuffle at the mouth of the hole and +the Great Spotted Woodpecker hurriedly left. +After this, all was quiet and the Green Woodpecker +eventually descended and entered the +hole. The Great Spotted Woodpecker, however, +returned again, but, after fluttering around +the hole, disappeared, leaving the Green Woodpeckers +in possession.</p> + +<div class="figcenter" style="width: 500px;"><a name="f281" id="f281"></a><img src="images/fig281.jpg" width="500" height="925" +alt="A battle between a pair of Green Woodpeckers +and a pair of Pied Woodpeckers for the +possession of a hole in an oak tree." title="A battle between a pair of Green Woodpeckers +and a pair of Pied Woodpeckers for the +possession of a hole in an oak tree." /></div> + + +<p class="underline">ERRATUM</p> + +<p class="center"><i>For</i> "pair of Pied Woodpeckers"<br /> + <i>read</i> "Great Spotted Woodpecker"<br /> +</p> + +<p>In this varied field of hostile behaviour +which we have explored, one feature stands +out prominently, namely, that the interest<span class='pagenum'><a name="Page_239" id="Page_239">239</a></span> +which a bird displays in other species varies +not only at different seasons but even from +hour to hour. I have used the word "nature" +as equivalent to "interest," and I have spoken +of the bird's nature changing or altering according +to the circumstances in which it was placed. +But its nature is its inborn constitution, and its +constitution cannot change from day to day, +still less from hour to hour. So that, in a sense, +and having regard to strict scientific accuracy, +it is misleading in this particular connotation to +say that the bird's nature changes.</p> + +<p>What then does happen? The instinct of +pugnacity must form just as much a part of +the hereditary make-up of the migrant, when +on migration, as when finally it reaches its +destination; still more must it form part of +the constitution of the Bunting when it leaves +its headquarters temporarily and joins the flock. +And, if it is there, the question arises as to +why it does not respond. Now every instinct +requires for its response a stimulus of an appropriate +kind, and, therefore, a reasonable view +to take would be that the necessary stimulus +was lacking. But this is a view which we +cannot uphold, because on all these occasions +an opposing male was present—and, so far as it +is possible to judge by observation, that is the +stimulus which in the main evokes a hostile +response. We must therefore look elsewhere +than in its direction for a reason which will +adequately explain the behaviour.</p> + +<p>Though it be true that every instinct<span class='pagenum'><a name="Page_240" id="Page_240">240</a></span> +requires for its functioning a stimulus of an +appropriate kind, yet it is also true that the +condition which will render it responsive must +be present. What we have then to consider is +whether the phenomena which we have explored +give us any clue as to the particular nature of +that condition. In the first place, we have the +general fact that the hostility is not confined to +a few species belonging to a few families, but +that it is of wide application—birds of prey, +Warblers, Woodpeckers, all supply us with +evidence which serves to show, in greater or +less degree, its nature and extent. Next, we +found that the hostility was peculiar to a +certain season—and that one the season of +reproduction. And if the question were asked: +What condition would then be most likely to +render the instinct susceptible, the answer that +would most certainly be given would be—the +presence of a female. And in reply to a +further question as to the particular nature of +the stimulus to which the instinct would +respond, we should be told—the presence of +another male of the same species. Now the +possible influence of the female on the course +of the male's behaviour was the subject of +inquiry in the second chapter, wherein we +endeavoured to explain the hostility between +males of the same species, and we came to +the conclusion that it was not alone sufficient +to account for the facts disclosed. Still +less likely, therefore, is it that her presence +can bear any direct relation to the hostility<span class='pagenum'><a name="Page_241" id="Page_241">241</a></span> +between different species, the more so since +the biological end of securing a mate is +definitely excluded. And we have something +in the nature of proof of the correctness of +this view in the fact that she accompanies her +mate when he joins the flock, and that there +his instinct is not susceptible to stimulation. +We then proceeded to examine certain cases +in which all the indications pointed to the fact +that the "will to fight" was present in only +one of the opponents; and we attached considerable +importance to this circumstance, because +we knew from experience that the same bird +which seemed to lack courage, could at other +times and in other situations be most aggressive. +If then we ask what condition was present on +the one occasion that was absent on the other, +we have no difficulty in finding a reply—on +every occasion on which the opponents appeared +to be unevenly matched, one was in occupation +of a territory and the other was not. And if +we inquire further as to which of the two was +the aggressor, the answer is again clear, namely, +the bird that occupied a territory. Finally we +considered some particular instances in which +the "will to fight" was present alike in both +opponents, and in which the battles were +protracted and severe.</p> + +<p>But the fact that a bird has established a +territory is not in itself sufficient to render its +hostile nature susceptible; it must be actually +in occupation if a response is to be elicited. +We reach this conclusion step by step: the<span class='pagenum'><a name="Page_242" id="Page_242">242</a></span> +behaviour of the migrant, that lacks the "will +to fight" when on migration but is pugnacious +when it has secured a territory, shows it; the +behaviour of the resident, which temporarily +joins the flock and is there sociable, shows it; +and it is shown also by the determination with +which both opponents fight when the question +of ownership of a station is in dispute. And of +all the facts we have reviewed, this is perhaps +the most important in relation to our present +subject, for it demonstrates that the change +from sociability to hostility is not merely an +incident of the sexual season, not merely an +indirect result of the functioning of the general +disposition which leads to the establishment of a +territory, but that it is intimately associated +with the whole process, and that the particular +part of the bird's nature which is concerned is so +nicely balanced that it will respond under one +condition and one only.</p> + +<p class="tb">Thus we are led to the only conclusion +which seems consistent with the facts, namely +that there is a relationship between the +"territory" and the hostility.</p> + +<p>If we are satisfied that all this warfare is not +merely an expression of an instinct which is +serviceable in another direction, what part does +it play in the whole scheme of reproduction?</p> + +<p>The young of many birds are delicate at +birth and unable to withstand exposure to cold, +and in the previous chapter we came to the conclusion +that the territory was serviceable in that<span class='pagenum'><a name="Page_243" id="Page_243">243</a></span> +it provided an adequate supply of food in the +vicinity of the nest, and thus obviated the +necessity of the parents being absent from them +for long. But manifestly no matter how active +a male may be in driving away members of +its own sex and kind, it will neither make +its position secure, nor insure a supply of food +for its young, so long as any number of +individuals of different kinds are allowed to +establish themselves in the same space of +ground. On the one hand, then, we have the +fact that there is constant strife between males +of close affinity, whilst on the other, we know +that many species require like conditions of +existence and are bound to assemble wherever +these conditions are suitable; and we can infer +that the territory would fail to serve its purpose +if no restriction were imposed upon the measure +of such assemblies.</p> + +<p>The question then arises: Does all this +warfare contribute towards the attainment of +reproduction? Not far from my house there is +a small water meadow, three acres in extent, +which for some years has been derelict and is +now overgrown with the common rush (<i>Juncus +communis</i>) and small alder trees. For three +successive seasons I watched the bird life of this +meadow, and more especially the Reed-Buntings +whose behaviour I was studying at the time. +In every respect the meadow was suitable for +this bird; there was an abundance of food and +numberless situations in which nests could be +placed. Each year all the pairs were successful<span class='pagenum'><a name="Page_244" id="Page_244">244</a></span> +in rearing one, if not two broods, yet the +number of pairs never exceeded five—the first +year there were three; the second year five; +and the third year four. In addition to the +four pairs of Reed-Buntings, there were in the +spring of 1915, six pairs of Whitethroats, one +pair of Lesser Whitethroats, four pairs of +Willow-Warblers, one pair of Sedge-Warblers, +two pairs of Grasshopper-Warblers, one pair of +Chiffchaffs, three pairs of Hedge-Sparrows, two +pairs of Tree-Pipits, one pair of Skylarks, one +pair of Whinchats, one pair of Flycatchers, two +pairs of Song-Thrushes, one pair of Blackbirds, +one pair of Redstarts, three pairs of Chaffinches, +and one pair of Wrens—in all, thirty-five pairs, +whose young were mainly dependent for their +living upon the insect life of that meadow and +the ground immediately surrounding it. If we +allow three young to each pair—and this would +take no account of second broods—we arrive at +the following result, namely, that one hundred +and five young and seventy adults had to be +supplied with food from that locality, which +would mean, if the search for food were strictly +limited to that meadow, that 83 square yards +would be allotted to each individual.</p> + +<p>Suppose now that the four male Reed-Buntings +had each admitted one other male, +and that they had secured mates, what would +have been the effect upon the whole community? +The four additional pairs with their young +would have represented twenty individuals, +which would have represented a decrease of<span class='pagenum'><a name="Page_245" id="Page_245">245</a></span> +8.5 square yards in the space allotted to each +individual. The pressure of the bird population +upon the means of support would then have +been materially increased; and not only the +Buntings, but the Warblers, Pipits, and all +the rest would have suffered. But the result +would have been the same if, instead of +the four additional male Reed-Buntings, four +males of other kinds had been allowed to +enter the marsh, and we can multiply the +number four until we arrive at a point when +the means of subsistence would no longer have +been adequate for the adults, still less for the +young. If, then, there were nothing to prevent +this happening, many of the birds in that +marsh would have no chance of rearing their +young successfully. Hence, if the territory is +adequately to serve the purpose for which we +believe it has been evolved, some provision must +have been included in the system to meet the +difficulty.</p> + +<p>There are three ways by which this may have +been accomplished—indirectly, by increasing the +size of the area occupied by each individual, +and thereby reducing the relative number of +each species; or directly, by rendering the +fighting instinct of the bird susceptible to +stimulation by individuals of other species; or, +possibly, by a combination of the two. There +were four pairs of Reed-Buntings in the marsh, +and their territories covered the whole of it. +But inasmuch as other insectivorous birds were +established there also, and found sufficient food<span class='pagenum'><a name="Page_246" id="Page_246">246</a></span> +to maintain both themselves and their families, +it is clear that the area these Reed-Buntings +occupied was in excess of that which they +would have required if they had been the sole +inhabitants. And such often appears to be +the case. Many a Warbler allocates to itself +a space of ground more than sufficient to supply +it with all that it needs; so, too, does the Finch, +or the Pipit, or the Falcon—if we take no +account of kindred species. Thus there is +reason to believe that, by limiting the number +of individuals in a given locality, this apparently +wasteful expanse of territory is serviceable in +that it provides against the pressure of the bird +population upon the available means of support +becoming too great. But though a reduction +in the numerical standing of the different species +would certainly follow from any increase in +the area occupied by the respective individuals, +and with even greater certainty would place +them in a more secure position as regards their +supply of food, yet, when we remember how +large a number are dependent upon a supply +of insect life for their young, we can understand +that it would not alone be a sufficient safeguard +against the dangers attendant upon overcrowding. +It is here, I believe, that we shall +find the true explanation of the hostility; it +roughly insures that the number of pairs in +any given area does not exceed the available +means of support, and indeed it is difficult to +imagine how such uniformity of distribution +as would free the young from the risk of<span class='pagenum'><a name="Page_247" id="Page_247">247</a></span> +exposure could be obtained without some such +control.</p> + +<p>Some birds, however, have no difficulty in +finding the necessary food for their young, yet +have great difficulty in finding a station where +they can rear their young in safety; and the +area each one occupies has been reduced +to the smallest proportions in order that the +maximum number can be accommodated. Here, +any increase in the size of the territory would +inevitably lead to the extinction of the race, +so that nothing stands between failure and +success except the ability of the bird to defend +its territory. If we study the bird population +at one of the breeding stations on the coast, +we find, generally speaking, that each kind of +bird inhabits a particular portion of the cliff; on +the lower ledges are the Guillemots and Kittiwake +Gulls; higher up are Razorbills and +Fulmars, and at the top, where the cliff is +broken and the face of the rock covered with +turf and soil, the Puffin finds shelter for its +egg. At the same time there is much overlapping; +the kind of ledge that suits a Razorbill +is equally suitable for a Guillemot or a +Fulmar, and so, no matter how successful the +Razorbill may be in establishing a territory +and preventing intrusion upon it by other +Razorbills, it will be all to no purpose if it +allows itself to be jostled out of its position +by a Fulmar. Hence, inasmuch as breeding +stations are limited and competition for territory +so severe, only those forms in which the fighting<span class='pagenum'><a name="Page_248" id="Page_248">248</a></span> +instinct responds freely to a wide range of stimuli +will be in a position to maintain a footing upon +the cliff.</p> + +<p>In trying to estimate the importance of the +hostility in its relation to the territory, we must +bear in mind that competition varies in different +seasons and in different localities. The surface +of the land is constantly undergoing modification, +partly owing to human and partly to physical +agency—forests are cleared; marshes are drained; +the face of the sea-cliffs is altered by the erosion +of the waves; here the coast may be locally +elevated, there locally depressed; and so forth. +Many of these changes are slow and imperceptible, +many can be observed in our own +lifetime. The timber is felled and the undergrowth +cleared in some wood, and the following +spring we notice a change in the character of +the bird population. Migrants which formerly +found in it no suitable accommodation now +begin to appear, and as the seasons pass by +and the undergrowth affords more and more +shelter for the nests and an increasing supply +of insect life, so their numbers increase until +the wood becomes an important breeding station, +resonant with the song of many individuals. +But slowly the growth increases; the bushes +pass into saplings and the saplings into trees, +and the undergrowth then disappears just +as surely as do the migrants which can no +longer find there the conditions which they +require.</p> + +<p>Or, as an illustration of the effect produced<span class='pagenum'><a name="Page_249" id="Page_249">249</a></span> +by natural agency, let me describe a change +which has taken place in a corner of Co. Donegal. +The promontory of Horn Head is bounded on +the west by extensive sand-hills, 100 ft. or more +in height. On the southern side it is divided +from the mainland by a channel, which narrows +down to 100 yards or so in width where it +fringes the sand-hills, and then widens out again, +covering an area of approximately 270 acres. +As far as is known in the memory of man, this +area has always been tidal. But in recent years +a change has taken place, and the blown sand +has silted up the channel, with the result that +this tidal area has been transformed into a +brackish lake. What has brought about the +change is not easy to determine. There is +evidence, however, of a slow alteration of the +level of the shore-line; for in the midst of the +sand-hills, situated 150 yards or so from the +present sea-margin, and running parallel with it, +there is an accumulation of pebbles some 3 feet +high by 4 feet deep. This raised beach is now +separated from the Atlantic by sand-drifts of +considerable height, and consequently there are +some grounds for believing that secular elevation +is taking place, which, if it be the case, will +account for the change in progress. Now the +effect on the bird population can be seen even +now, and will doubtless become more apparent +as the years pass by. Sand-Martins used to find +plenty of places to breed amongst the sand-drifts, +and moreover do so still. But their +nesting sites are constantly changing and dis<span class='pagenum'><a name="Page_250" id="Page_250">250</a></span>appearing, +and the breeding-place of one colony, +that was situated in the bank of a stream twelve +years ago, is now buried 10 feet or more below +the surface of the sand. The area that was once +tidal, but is now a brackish lake, is fed by +mountain streams, and as the fresh water +predominates, so in course of time will it become +fringed with vegetation; and instead of the +flocks of Curlew, Dunlin, and other waders that, +at low water, resorted there to feed, Coots will +fight with one another for the possession of +territories, and the Wild Duck will teach her +young to seek their food.</p> + +<p>In whatever direction we turn, we find +that many breeding grounds are subject to +incessant change. Ancient haunts disappear, +new ones come into being, a change which +makes life impossible for this bird, as likely +as not benefits that one, and so on. There +is no stability. Hence in any given district +each recurring season there must needs be a +large number of individuals which are obliged +to seek new stations, and if there were no +control over their distribution, if each one +were free to establish itself wherever it chanced +to alight, this locality might be overcrowded +and that one deserted; and, bearing in mind +how many species there are that require similar +conditions of existence, we can infer that the +successful attainment of reproduction would +become impossible for many of those individuals +so long as each species was indifferent to the +presence of the others. On the other hand, if<span class='pagenum'><a name="Page_251" id="Page_251">251</a></span> +there were no control over the range of the +intolerance, the smaller bird would have no +chance in competition with the larger, and it +is doubtful whether the larger would gain an +advantage commensurate with the energy it +would expend in ridding its area of the smaller. +I have described battles in which the opponents +were only distantly related; for instance, the +Moor-Hen will attack almost any bird—Partridge, +Lapwing, or Starling—that approaches its +territory even temporarily. Nevertheless the +antagonism between kindred forms is more +prevalent, and, as a rule, characterised by more +persistent effort; and thus it seems as if the +susceptibility of the fighting instinct has its +limitations, the degree of the responsiveness +being dependent upon the affinity of the +opponents.</p> + +<p>Suppose now that we take an area inhabited +by a number of different species requiring like +conditions of existence, divide it into three +sections, and imagine that in one they were all +sociable, that in another they were all hostile, +and that in a third those which were closely +related were intolerant of one another. Let us +suppose further that each one of them was +represented by the full number of individuals +that the law of territory would allow. In +the first section an individual would establish +itself, and, becoming intolerant of its own +kind, would exercise dominion over an area +roughly sufficient, providing conditions were +normal, to insure an adequate supply of food for<span class='pagenum'><a name="Page_252" id="Page_252">252</a></span> +its young. But it would take no account of +other species, and since any number might +occupy the same ground, the fact of its having +established a territory would not alone suffice to +render its supply of food secure. Success in the +attainment of reproduction would then become +largely a matter of chance, depending upon the +number of individuals that happened to settle in +this place or in that. In the second section +there would be perpetual warfare; for whereas +the appropriate organic condition which leads to +pairing arises in different species at different +times, fresh claimants to occupied ground would +constantly be appearing, and the efforts of the +inhabitants to preserve their boundaries intact +would have to be maintained throughout the +whole period of reproduction; and while the +stronger or more persistent forms would be +more likely to breed, they would do so at the +expense of their young, to which they would be +unable to devote proper attention, and with an +expenditure of energy that would reflect itself +upon the future of the race. But the conditions +of life in the third section would be such as +would be more likely to yield good results. +The relations of the different members of the +community would be more evenly balanced, for +a male would only be called upon to compete +with those of its own size and strength. Thus, +on the one hand, accommodation would be so +divided as to secure the breeding of the maximum +number of individuals with the minimum +of expenditure of energy, whilst on the other,<span class='pagenum'><a name="Page_253" id="Page_253">253</a></span> +any undue pressure upon the available means of +subsistence would be prevented.</p> + +<p class="tb">There can be no question that in the latter +section a higher percentage of individuals would +succeed in rearing offspring. And so, by reason +of the fighting instinct being more susceptible +or less susceptible according to the affinity of +the opponents, a control is established which, +while preventing unnecessary extension of warfare, +allows for sufficient extension to render the +biological end secure.</p> + +<p>These, then, are the facts—this the conclusion +which can be drawn from them. It may, +however, be said of these facts, as it has been +said, with even less justification, of the battles +between individuals of the same species, that +they do not afford evidence of genuine hostility. +No doubt there are many naturalists who could +supplement these facts with others in which the +conflicts resulted in bodily injury, or terminated +fatally, or at least were of a more determined +kind. But I have already drawn attention to +the fact that, so long as a definite result is +attained, the severity of the struggle and the +amount of injury inflicted are matters of small +moment. Let us, however, run over the substance +of the argument, and then briefly refer +again to this point of view.</p> + +<p>After enumerating instances of hostility, +sufficient in number, so it seemed, to constitute +reasonable ground for the belief that they had +a part to play in the life-history of the<span class='pagenum'><a name="Page_254" id="Page_254">254</a></span> +individual, the two questions we set ourselves +to examine in this chapter were: Is there any +circumstance in the life behaviour of the +individual with which the hostility can be +definitely related; and, will the hostility lead +to the securing of a greater measure of success +in the attainment of reproduction?</p> + +<p>Many different species assemble together in +winter and roam from place to place in search of +food. But in spring their behaviour undergoes +a remarkable transformation; they avoid one +another and become quarrelsome, so much so +that whereas the outstanding feature of the +winter is sociability, that of the spring is +hostility. With this general fact before us, +we proceeded to investigate this change of +behaviour still further. First of all we took +the case of a migrant, and, comparing its +behaviour, as it journeyed, with that when +finally it reached its destination, we found +that the bird which was notoriously pugnacious +when in occupation of a territory betrayed no +interest in other species as it travelled to the +accustomed breeding ground. Not only so, but +even though it was attacked, we found that +its pugnacious instinct still failed to respond. +Here, however, it may be contended, and with +reasonable justification, that in the interval +which elapses before the ultimate destination +is reached, some change in the organic condition +of the bird may occur which will account +for its altered behaviour; or, it may be urged, +with no less justification, that whereas on<span class='pagenum'><a name="Page_255" id="Page_255">255</a></span> +migration the bird is unpaired, when the +destination is reached it is probably in possession +of a mate and is therefore quarrelsome. +Now, at the most, the interval can only be +a matter of a few days, and it is unlikely +that organic changes sufficient to bring about +so important an alteration of behaviour could +occur in so short a time, still less likely that +they could be timed to come into functional +activity just at the moment when the bird +reaches its breeding ground. And with regard +to the suggestion that the change can be +accounted for by the presence of a mate, we +shall do well to remember not only that males +as a rule precede the females by some days, but +that a male may even remain in its territory, +mateless, for some weeks, and yet display +hostility.</p> + +<p>Nevertheless the case of the migrant did not, +by itself, afford sufficient evidence upon which +to base any conclusion. We therefore inquired +into the behaviour of some of the residents at a +corresponding period. The Bunting served as +an illustration. Early in the season it establishes +a territory, and because food is then +scarce it is forced to seek it elsewhere than on +the small plot of ground which it has acquired; +and so it makes its way to some spot where +the supply is abundant, and there, meeting +with other species bent on a similar errand, +forms with them a flock. Part of its time is +then spent in the territory and part on the +feeding ground, and between these two points a<span class='pagenum'><a name="Page_256" id="Page_256">256</a></span> +highway is formed by the bird passing constantly +to and fro. But the attention which it pays to +other species is very different on these two +occasions—when in the territory it is intolerant +of strangers, but when it accompanies the flock +it displays no interest in their movements. +From hour to hour its nature seems to change. +But, as we saw, the inborn constitution of the +bird cannot change, and therefore we came to +the conclusion that an explanation of the altered +behaviour was to be found in the fact that the +pugnacious instinct is only rendered susceptible +under a certain condition. So that all the +evidence tended to confirm the impression which +we had gained from the course of events in the +life of the migrant, namely, that the hostility +bears a direct relation to the occupation of a +territory.</p> + +<p>Finally we were led to inquire whether the +hostility was serviceable in promoting the +welfare of the individuals. We saw that many +different species require similar conditions of +existence, that ancient breeding haunts disappear +and that new ones come into being, and +that in the ordinary course of events such +species must often assemble in the same area for +the purpose of reproduction. So that even +though a male might be successful in protecting +its ground from intruders of its own kind, yet it +might still fail to rear offspring, just because it +happened to choose a position in which other +kindred forms had gathered. Hence if the +territory is adequately to serve its purpose,<span class='pagenum'><a name="Page_257" id="Page_257">257</a></span> +some control over the local distribution of +species is of paramount importance. Nevertheless, +if all the different forms that require similar +conditions of existence were intolerant of one +another in a like degree, the smaller bird would +have no chance in competition with the larger. +This, however, is not the case. Some, as we +saw, arouse little or no animosity in others, in +fact the more closely related the rivals, the more +responsive their pugnacious nature seems to +become.</p> + +<p>To return now to the view that the fighting +is not really serious, but, on the contrary, that it +is either vestigial and has no longer any part to +play in furthering the life of the individual, or +that it is a by-product of the seasonal sexual +condition to which no meaning can be attached. +First, there is the relationship with the territory, +and this, it seems to me, is a fact of some +importance; for if the fighting were merely an +exuberant manifestation of sexual emotion, one +would expect to find it occurring under all +conditions, and not merely under one particular +condition in the life of the bird. The hostility +is too widespread, however, and too uniform in +occurrence for us to suppose that it has no root +in the inherited constitution of the bird; and if +it served some useful purpose in the past, the +instinct might still persist, so long as it were not +harmful. Thus the view that the behaviour is +vestigial is not perhaps unreasonable. But +manifestly it makes no difference whether it be +vestigial or a by-product of sexual emotion,<span class='pagenum'><a name="Page_258" id="Page_258">258</a></span> +whether the battle be fierce or so trivial as to +appear to us to be more in the nature of "play," +so long as some change in the relative prospects +of the opponents is the result.</p> + +<p>For us, then, the main consideration lies in +the question: Is the behaviour serviceable +now in furthering the life of the individual? +Whether the evidence which we have examined +affords sufficient ground for the belief that the +hostility is genuine and has a part to play in the +whole scheme of reproduction, each must judge +for himself.</p> +<hr /> +<p><span class='pagenum'><a name="Page_259" id="Page_259">259</a></span></p> +<h3>CHAPTER VII</h3> + +<h4>THE RELATION OF THE TERRITORY TO +MIGRATION</h4> + + +<p>Coincident in time with the growth of +appropriate conditions in the environment, +organic changes take place rendering certain +instincts susceptible to stimulation; and the +stimulus being applied, the Warbler leaves the +country wherein it had passed the winter and +finds its way back, with apparently little +difficulty, to the district in which it was reared +or had previously reared offspring. What is +the nature of these changes and of the impulse +which is first brought into functional activity; +whence comes the stimulus; and what directs +the bird on its journey—these are all different +aspects of one great problem, the problem of +migration. I do not propose to discuss all these +various aspects, for indeed I have no suggestions +to offer which are in the least likely to be +helpful, but I seek rather to ascertain whether +the phenomena which we have explored bear +any relation to the problem as a whole; +whether, that is to say, the competition for +territory and all that appertains to it can have<span class='pagenum'><a name="Page_260" id="Page_260">260</a></span> +supplied the conditions under which, in the +process of time, this complex and definite mode +of behaviour has evolved.</p> + +<p>We are sometimes told that we must seek +the origin of migration in the physical changes +that have occurred in the ancient history of the +earth—in glacial conditions which gradually +forced birds to the south, or in the "stability of +the water and mobility of the land" which +brought about a gradual separation of the feeding +area from the breeding area—and which +continued for a sufficient length of time to +lead to the formation of an instinct, and that +the instinct persists because it is serviceable +in promoting the welfare of the race. But +when we consider the lapse of time, and the +changes that must have occurred in the character +of the bird population—the appearance of new +forms and the disappearance of the old, the ebb +and flow of a given species in a given area—and +bear in mind that, notwithstanding this, the +migratory instinct, if not stronger, is assuredly +no less strong, and the volume of migration, if +not greater, is assuredly no less; in short, that +the whole phenomenon is progressive rather +than retrogressive, we shall find the view that +the instinct owes its origin to conditions which +no longer exist, receives but little encouragement.</p> + +<p>I doubt not that, throughout the ages, +geological changes have been an important +factor in directing or limiting the scope of +migration, and moreover are so still; just as<span class='pagenum'><a name="Page_261" id="Page_261">261</a></span> +climatic changes and the relative abundance or +scarcity of enemies have influenced the course +of its evolution. These are all contributory +factors operating in the external environment. +But there are, besides, internal factors which +form part of the inherited constitution of the +bird, and, being passed on from generation to +generation, afford the conditions under which +migration is constantly being renewed. It is, I +believe, in this field of organic change and +relationship that the conditions of origin must +be sought.</p> + +<p>Just as the moth in passing from the rudimentary +to the perfect condition runs through a +series of changes, each one of which is marked +by a typical behaviour response adjusted to +meet some particular circumstance in the +external environment, so the annual history of a +bird displays an ordered routine, each phase of +which can be observed to correspond with one of +the successive changes in the environment. In +almost every direction, we find that this routine +is characterised, in broad outline, by great +uniformity; so much so that, providing we +know the history of one species, we can forecast +with no small degree of certainty the general +course of behaviour of other members of the +family. But only the <i>general</i> course. There is +endless variation in just the particular way in +which the behaviour is adapted to meet the +needs of particular species—the major details +may be said to be specific, the minor details +varietal.</p> + +<p><span class='pagenum'><a name="Page_262" id="Page_262">262</a></span>Now it is that part of the behaviour routine +which has reference to the relationship between +one bird and another upon which, for the time +being, I wish to dwell; for the interest that +A displays in B is by no means always the +same—it changes according to the season, and +this change can be observed to be uniform +throughout a wide range of species.</p> + +<p>In winter, in whatsoever direction we turn, +we observe not only that different individuals +but that different species also collect together +in flocks. And since food at that season is not +always easy to obtain, and, moreover, is only to +be found in certain situations, which are limited +both in number and extent, it would seem that +such assemblages are in the main determined +by accident. No doubt the abundance or the +scarcity of food does determine the movements +of birds, and hence to that extent may be held +to account for the flocks. But we shall but +deceive ourselves if we think that it is the sole +or even the principal reason, or that the situation +is in no wise affected by internal factors. The +behaviour of the individual in relation to the +flock bears ample testimony to the presence of +a gregarious impulse which derives satisfaction +from the fact of close association.</p> + +<p>As an illustration, let us take a bird whose +movements are easily watched, and in whose +hereditary constitution the impulse to which I +allude seems to be strongly implanted—the +Curlew. When the breeding season is over, +Curlew leave the mountain and the moor and<span class='pagenum'><a name="Page_263" id="Page_263">263</a></span> +return to the coast or tidal estuaries for the +remainder of the year. Here, at low water, they +find an abundant supply of food—crustaceans +amongst the sea-weed upon the rocks, and lobworms +(<i>Arenicola piscatorum</i>) in the mud as the +tide advances or recedes. But when the tide is +full, they retire to those parts of the shore that +remain uncovered—to isolated rocks, or to sand-dunes, +or it may even be to pasture-land in the +neighbourhood. During this period of repose +large numbers of individuals gather together on +a comparatively small space of ground. They +are not constrained to do so by any shortage of +accommodation, nor by any question relative to +food, nor, for the matter of that, by any circumstance +in the external environment; they are +brought together solely, this at least is the +impression that one gains, by some inherited +impulse working towards that end. And their +subsequent course of behaviour tends to confirm +that impression. For if we watch the gathering +together of the different units of which the flock +is composed, and study more particularly the +emotional manifestation which accompanies their +arrival and departure, we shall find that the +coming of a companion arouses some emotion +which is expressed by a vocal outburst that +sweeps through the flock.</p> + +<p>Now each call, and the Curlew has a great +variety, is not only peculiar, generally speaking, +to certain occasions, but is accompanied by a +specific type of behaviour, whence we can infer +in broad outline the type of emotion which is<span class='pagenum'><a name="Page_264" id="Page_264">264</a></span> +aroused. Thus we come to recognise fear, anger, +or sexual emotion, by just the particular sound +which is emitted. But even if we are going +too far in referring particular calls to particular +emotions, we can, without a doubt, divide them +into two broad categories—those which are +pleasurable and those which are the reverse. +And we need have no hesitation in placing the +particular call to which I allude in the first of +these two categories, not only on account of the +nature of the sound produced, but because the +activities which are aroused are not such as +normally accompany irritation. This is well +seen if the behaviour of different individuals +be closely observed. After resting on one leg +for some time, first one and then another is +seized with cramp, and running a few yards +in an ungainly way, bumps up against its companions +as if it had not full control over its +movements. Its behaviour produces irritation +which is expressed by a vocal outburst, and +followed by actions the meaning of which is +clear. Moreover, the call is taken up by +other individuals and sweeps over part of the +flock as does the greeting. But the nature of +the cry is entirely different from that which +greets the arrival of a companion—humanly +speaking it is a passionate and impatient utterance, +the height of displeasure. The arrival, +then, acts as a stimulus to something in the +inherited constitution which is expressed in, and +presumably is satisfied by, this vocal outburst; +and, since the bird that arrives joins also in the<span class='pagenum'><a name="Page_265" id="Page_265">265</a></span> +chorus, there is reason to think that the impulse +which determines its movements is similar to +that which is temporarily aroused in the flock.</p> + +<p>Apart, however, from the evidence derived +from the affective aspect of the operation of the +instinct, the general course of behaviour lends +support to the view that the assemblies are +determined by internal factors, and are not +merely the outcome of circumstances in the +external environment. Observe, for example, +the manner in which the flock is built up. +Single individuals are content to rest alone so +long as no assembly is in sight, but they are +drawn towards their companions directly the +opportunity arises, just as surely as the smaller +aggregation is drawn towards the flock; and so, +as the flock increases, it gradually absorbs all +the lesser flocks and smaller parties, for the +greater the flock the greater the attraction +seems to be; and different individuals appear +to gain some satisfaction from being in close +bodily contact with one another.</p> + +<p>When the Curlew flies to that part of the +mud-flat which is first exposed by the receding +tide, and there associates with others, it does +not then do so because it has any interest in its +fellows, nor because they serve as an attraction, +but because it is constrained by hunger—in +other words, the association is determined by +accident. But when, during periods of repose, +it sees a flock, flies to it, and takes up a position +in the midst of it, it does so not because suitable +accommodation is lacking—not therefore because<span class='pagenum'><a name="Page_266" id="Page_266">266</a></span> +of external constraint—but because it derives +some pleasure from satisfying something in its +organic complex. We speak of this behaviour +and of the emotion which characterises it as the +<i>gregarious instinct</i>: by which we mean that the +inherited nature of the Curlew, as a tribe, is so +constituted that, given the appropriate internal +conditions and adequate external stimulation, +every individual will respond in a similar manner—that +is, the behaviour is primarily determined +by racial preparation. This is what we mean +by the <i>gregarious instinct</i> biologically considered. +We may resolve our own experience in relation +to the crowd into its simplest constituents, +project our own primitive feelings into the +Curlew, and say that the bird feels uneasiness +in isolation and satisfaction in being one of the +flock. But in truth we know nothing, save by +analogy, of the correlated psychical state. All +the knowledge we possess is derived from a +study of the objective aspect of the behaviour, +which in simple terms may be expressed thus: +the individual is drawn towards its companions; +there is a relation between the size of the flock +and the strength of the attraction; and all +Curlew behave similarly under similar circumstances.</p> + +<p>This instinct controls the movements of +many birds from early autumn to the commencement +of the breeding season. And so +powerful is the control that the individual is +suppressed and its activities subordinated to the +welfare of the community as a whole. Flocks<span class='pagenum'><a name="Page_267" id="Page_267">267</a></span> +of Waders roam about the tidal estuaries in +search of food, and different kinds of Gulls +assemble there and preen their feathers or sleep; +Warblers alter their mode of life, and in the +osier bed, or amongst the elders, seek their food +together in peace; Finches, Buntings, Pipits, +and Wagtails, though food is everywhere +abundant, gather themselves together respectively +into bands which, as winter approaches, +grow into flocks and even into composite flocks; +and as the Warblers leave for the south, so their +places are filled by flocks of Thrushes and +Finches from the north. In whatever direction +we turn, when the days begin to shorten, it is +the community, not the individual, that thrusts +itself upon our attention; and throughout the +winter continues to be the outstanding feature +of bird life.</p> + +<p>With the approach of the breeding season +we witness that remarkable change which I have +endeavoured to make clear in the previous +chapters—the disintegration of the flock and +the reinstatement of the individual. Instead +of continuing with the flock, the individual now +goes forth to seek the appropriate breeding +ground; and having arrived there, is not only +content to remain in isolation, but so behaves +that isolation is insured. Intolerant of the +approach of a stranger, intolerant even of the +approach of the very members of the community +whose companionship was previously welcomed, +it not only fights to maintain the position it has +selected, but fights indeed for the possession of<span class='pagenum'><a name="Page_268" id="Page_268">268</a></span> +ground already occupied, and, until reproduction +is completed, asserts its individuality and exercises +dominion over its territory. What, then, +is the prospective value, biologically considered, +of the changing interest that A displays in B, +and to what will such changes lead? These are +the questions to which we will now direct +inquiry.</p> + +<p>The annual life-history of a bird is in broad +outline conditioned by two powerful and at first +sight opposing impulses—the one to live in +society, the other to live solitary. But, manifestly, +a bird cannot be governed by opposing +impulses. It has but one character, within +which, according to the season and the circumstances, +different impulses predominate. But +these impulses, no matter how different they +may appear to be, have their respective parts to +play in furthering the life of the individual. +Hence they cannot oppose, though they may +conflict, if the resultant behaviour contributes +towards survival.</p> + +<p>The majority of birds live to-day in constant +danger from predatory species, and that this +danger was still greater in bygone ages there +can be but little doubt. A curious mode of +behaviour of the Curlew, Whimbrel, and Godwit +demonstrates this, for it must be the outcome +of the necessity for constant watchfulness. +Whilst resting with its head turned back and +its beak buried in the feathers of the mantle, +the bird constantly moves the axis of its body, +so that an observer, if placed in a direct line<span class='pagenum'><a name="Page_269" id="Page_269">269</a></span> +behind it, sees at one moment the right eye +and at another the left. No movement of the +feet or of the legs is perceptible, and the shifting +of the body continues whether the eyes are +open or closed. This body movement enables +the bird to survey a much larger area of ground +than it would otherwise be capable of doing, +and thus adds to its security. As far as my +experience goes, the movement is less evident +amongst the members of a flock than when +an individual is resting alone, or even with a +few companions, which may be due to the fact +that since some members are always awake +and watchful, a bird of prey would have more +difficulty in approaching a flock unawares than +it would have in approaching a single individual. +With the greatest ease a Sparrow-Hawk can +pick up a Thrush as it feeds on the meadow +by itself, but if it attempts to seize one of a +flock, the chances are that its approach is +signalled and that its prey escapes. And not +only do the different members give warning +one to another of the approach of danger, +but they also combine to harass or even to +drive away an enemy. So that there can be +no doubt that the gregarious instinct is serviceable +in promoting the welfare of the race, and +has, as its end, the preservation of the individual +in order that it may take its share at the +appropriate time in procreating its kind.</p> + +<p>In winter, then, the individual loses its +individuality and is subordinated to the welfare +of the community, whilst in spring it regains<span class='pagenum'><a name="Page_270" id="Page_270">270</a></span> +its individuality, and all its inherited instincts +which then come into operation lead to its +isolation from the flock. The impulse to seek +isolation is dependent upon internal organic +conditions which are peculiar to a certain +season; whereas the gregarious impulse depends +upon internal organic conditions which inhere +at all times, though its functioning is inhibited +by the functioning of the former impulse. The +evidence which leads to this conclusion is to +be found in the fact that a male often deserts +its territory temporarily and joins the flock, +where it remains at peace with its companions—an +aspect of behaviour which we have discussed +on various occasions. The former impulse becomes +dominant in the spring owing to its +innately superior strength; the latter becomes +dominant in the autumn because the organic +condition which determines the functioning of +the former then subsides. The impulse to +seek the appropriate breeding ground and to +dwell there would seem to be the strongest +of all the impulses save one—the sexual. +When, however, I speak of the sexual, I +refer to the actual discharge of the sexual +function, which is the consummation of the +whole process. But the territory and all that +appertains to it is part of that process—the +search for the breeding ground, the dwelling +there, and the intolerance of intrusion are but +different stages, each one of which must +have an impulse peculiar to it; and since the +completion of the sexual act can only be<span class='pagenum'><a name="Page_271" id="Page_271">271</a></span> +successfully accomplished providing that success +is attained at every stage, the probability is +that, of the impulses concerned, one is neither +more powerful nor less powerful than another.</p> + +<p>So that we have two impulses operating at +different seasons and guiding the behaviour +into widely divergent channels. But though +the proximate end to which the behaviour is +directed is apparently different, there are not +two biological ends in view, but one—the +attainment of reproduction; and the changes +that we witness are not contrary but complementary, +and their prospective value lies in the +circumstance that they contribute towards the +preservation of the race.</p> + +<p>If, then, every male is driven by inherited +impulse to seek the appropriate breeding ground +each recurring season; if, having arrived there, +it is driven to seek a position of its own; if, +in order to secure isolation it is obliged to +attack other males or to ward off the attacks +of intruders; if, in short, success can only be +attained providing that the inherited nature is +so adjusted that the bird can accomplish all +that is here demanded—what will be the general +result? That the individual will rear its offspring +in safety and that they will inherit the +peculiarities of their parents, enabling them, +in their turn, to procreate their kind; all this +will certainly follow. We are not concerned, +however, at the moment, with the direct effect +upon the individual, but with the consequences +that will accrue to the species as a whole.</p> + +<p><span class='pagenum'><a name="Page_272" id="Page_272">272</a></span>Now certain facts are presented to observation +which enable us not only to understand the +nature of the change that is wrought in the +history of the species, but to foreshadow, with +no small degree of certainty, the extent of that +change. I suppose that it has come within the +experience of most of us to observe, at one time +or another, the ebb and flow of a given species +in a given district. Some favourite haunt is +deserted for a year, or for a term of years, and +is then revisited; or, if it is always occupied, +the number of inhabitants fluctuates—plenty +of pairs in this season, only a few in that. +Many intricate relationships, both external and +internal, contribute towards this state of affairs. +Fluctuation in a downward direction, or +temporary extinction, is brought about by +changes in the physical world, by changes in +the available supply of food, by the increase +of enemies, or by adverse climatic conditions; +whilst fluctuation in an upward direction, though +due indirectly to a combination of circumstances +in the external world favourable to the survival +of large numbers of individuals, is directly +determined by the impulse to seek isolation. +As individuals of different species establish +themselves, and form kingdoms and lesser +kingdoms, we can watch the gradual quickening +into life of moorland and forest and we can +observe the manner in which it all comes to +pass. Males that for weeks or months have +lived in society, drifting from locality to locality +according to the abundance of food or its<span class='pagenum'><a name="Page_273" id="Page_273">273</a></span> +scarcity, now set forth alone and settle first here +and then there in search of isolation. Lapwings +settle in the water meadows, and, finding themselves +forestalled, pass on in search of other +ground; Blackbirds arrive in a coppice or in a +hedgerow and, meeting with opposition, disappear; +and the Curlew, wandering with no +fixed abode but apparently with a fixity of +purpose, searches out the moorland where it can +find the particular environmental conditions to +which its inherited nature will respond. In +fact, wherever we choose to look, we can +observe in a general way the gradual appropriation +of breeding ground; and if we fix our +attention upon particular males, we can watch +the method by which success or failure is +achieved.</p> + +<p>On more than one occasion I have watched +the efforts of Reed-Buntings to appropriate +territories in a marsh that was already inhabited. +Sometimes their efforts met with success, at +other times with failure. In the former case, +the males, whose ground was intruded upon, were +severally forced to yield part of their holding +and were thus left in possession of a smaller +area. The success of the intruder seemed to +depend upon persistent determination, rather +than upon superior skill in battle. Recently I +had an opportunity of observing the intrusion of +a male Willow-Warbler upon ground already +occupied. By persistent effort it succeeded in +appropriating one half of the territory of its +rival. The intruder occupied some trees on the<span class='pagenum'><a name="Page_274" id="Page_274">274</a></span> +outskirts of the territory it was invading, and +used them as a base from which it made +repeated efforts to enter the ground of its rival. +These efforts were time after time frustrated. +No sooner did it leave its base than it was seen +and intercepted, or else attacked; and no matter +from which direction it attempted to effect an +entrance, its efforts, for a time, were all to no +purpose. The fighting was of a determined +character, and after each attack the owner of +the territory showed signs of great excitement, +and, sitting upright upon a branch, spread and +waved its wings, which is the specific emotional +manifestation during the period of sexual +activity. Eventually the intruding male succeeded +by persistent effort in appropriating part +of the occupied ground.</p> + +<p>Thus we can actually witness the efforts of +the individual to isolate itself from members of +its own kind, and can observe the immediate +consequences that follow from success or from +failure. And from these consequences we can +infer that, within a certain range but in accordance +with the relative abundance of the species +that dwell in it, every corner of the available +breeding ground will be explored and every +situation that evokes the appropriate response +will be occupied. Moreover, since the annual +dispersion is not merely a repetition in this +season of that which occurred in a previous one, +a progressive increase in the area occupied will +follow. Yet, if the majority of species desert +their breeding ground so soon as reproduction is<span class='pagenum'><a name="Page_275" id="Page_275">275</a></span> +ended, how can this be? An answer to the +question will be found in the fact that a bird +has an innate capacity to return to the neighbourhood +of its birthplace, or to the place +wherein it had previously reared offspring—which +means that the results of prior process +persist as the basis and starting-point of +subsequent process.</p> + +<p>Bearing then in mind that the seeming +peace in bird life around us in the spring is +but the expression of transitory adjustments in +the distribution of individuals and of species; +bearing in mind how widespread is the search for +isolation each recurring season, how frequently +the search leads to competition and competition +to failure, and how failure implies a renewal of +the search; bearing in mind that situations, +which appear to be eminently suitable for +breeding purposes, are passed by year after year +and remain unoccupied, just because, for reasons +which have yet to be ascertained, the environment +fails to supply some condition which is +essential if the inherited nature of the bird is to +respond—can there be any doubt that the +general result of the functioning of the disposition +will be expansion; or, since no limit is +placed upon it from within but only from +without—that is, by unfavourable circumstances +in the external world, that the expansion will +not merely be in one direction but in every +direction?</p> + +<p>If now, when reproduction is ended, all +the impulses relating to it die away, and the<span class='pagenum'><a name="Page_276" id="Page_276">276</a></span> +gregarious instinct again predominates, what are +the consequences to which this change will +lead? Just as the consequences which flow +from the functioning of the former impulse are +accessible to observation, so likewise can we +observe the change that is wrought by the latter +impulse. The process is a gradual one. Less +and less attention is paid by the individual to +intruders, more and more is it disposed to pass +beyond its accustomed limits. Little by little, +accompanied by its young or without them, as +the case may be, the bird deserts its territory +and wanders out into the wilderness. Here it +associates with others, and finds in them a new +interest and, I doubt not, a new enjoyment. +All this we can observe as it takes place. But +just as there is an innate capacity to seek, in the +spring, the place where the pleasures of breeding +had formerly been enjoyed, so we are bound to +infer the existence in the adult of an innate +capacity to revisit the former area of association; +and this capacity will strengthen and confirm the +gregarious instinct and set the direction of the +general course of movement.</p> + +<p class="tb">We have seen, then, that the interest displayed +by one bird in another changes with +the seasons; we have seen that it is so modified +as to be in useful relation to different environmental +circumstances; as far as possible we +have traced out the consequences, and have +reached the conclusion that the change of +behaviour must, on the one hand, lead to +expansion, and on the other, to contraction;<span class='pagenum'><a name="Page_277" id="Page_277">277</a></span> +and we have seen that this conclusion is in +accord with the facts of observation—that is the +general result of our inquiry into the functioning +of the two powerful impulses, the impulse +associated with the disposition to secure a +territory and the gregarious impulse.</p> + +<p>The phenomenon of migration embraces a +number of separate problems, each one of which +presents features of great interest and of still +greater difficulty. On some of these problems +I do not intend to touch; I seek only to +ascertain whether the impulses that are concerned +in the securing of a territory, and in the +search for society, bear any relation to the +problem as a whole. I hold that the origin of +migration is not to be found merely in conditions +peculiar to a remote past, but that the conditions +inhere in the organic complex of the bird, +and are thus handed down from generation to +generation. Starting with this assumption I +examined the behaviour which normally accompanies +the seasonal life-history of the individual, +and found, in that behaviour, manifestations of +cyclical change leading to definite biological +consequences. I now propose to inquire whether +those consequences are such as might, in the +course of time, give rise to the seasonal change +of abode.</p> + +<p>We are apt to think of migration in terms of +the Warbler that enlivens our hedgerows in the +spring after travelling hundreds of miles from +the south, or of the Redwing that comes from<span class='pagenum'><a name="Page_278" id="Page_278">278</a></span> +the far north and seeks its food during the +winter on the meadows, or perhaps of the +American Golden Plover that each year covers +a vast expanse of ocean in its journey from its +breeding ground. The length of the distance +strikes the imagination and constrains us to +focus attention upon the extremes.</p> + +<p>But migration is of much wider significance +than is here represented. I sit beside the River +Severn in April and watch Swallows, Tree-Pipits, +and Yellow Wagtails passing in twos +and threes, in small parties, or it may be in +small flocks; and I observe that while some +establish themselves in the neighbourhood, +others pass on. Or I watch Herring-Gulls +returning to the breeding station at Bolt Head, +an endless stream of individuals coming from the +east as far as eye can reach; following them for +some miles inland I see them still, first as specks +upon the horizon, then passing beside me as +they beat their way slowly against the strong +south-westerly winds, and finally disappearing +from view in the direction of the cliffs. Or +again, I watch Buntings and Finches deserting +the flock and seeking stations in the marsh, or +amongst the furze-bushes on the common, or in +the spinneys. In each case the proximate end +of the behaviour is alike—wherein then lies +the difference? Only in the distance which +separates the territory from the area in which +the birds formerly associated. And intermediate +between the extremes, I doubt not, if we had +a sufficient body of observations, that we should<span class='pagenum'><a name="Page_279" id="Page_279">279</a></span> +find numerous gradations, the lesser merging +step by step into the greater. Is the Swallow +a migrant and the Herring-Gull not; is the +Tree-Pipit a migrant and the Bunting not; +must a bird cross many miles of sea or of +land before it can be considered a migrant; is +the length of the distance traversed a criterion of +migration? Surely not. The distance traversed +is merely a collateral consequence of the process +as a whole.</p> + +<p>The annual life-history of a bird presents, as +we have seen, two distinct phases—the one in +which the individual dominates the situation, +the other in which it is subordinated to the +welfare of the community. Let us take these +two phases separately and endeavour to see how +they may have influenced the seasonal movements; +and first let us take the more important +of the two, namely that one which is directly +concerned in the continuance of the race.</p> + +<p>In this phase we must consider the three +factors to which allusion has already been +made:—(1) the internal impulse, (2) the innate +ability to return to the former breeding ground, +(3) the conditions in the external environment. +These three work in close relation and, as I shall +endeavour to show, lead to important results.</p> + +<p>(1) If there were nothing in the inherited +nature beyond an impulse to seek the breeding +ground, if, that is to say, when the appropriate +locality were reached, the bird took no further +interest in the developing situation, the attainment +of reproduction would become largely a<span class='pagenum'><a name="Page_280" id="Page_280">280</a></span> +matter of chance. A male in a congested +district, having no incentive to seek fresh +ground, would remain inactive until a female +happened to cross its path and stimulate its +sexual impulse, when its activity would take +another form. Hence some districts would be +over-populated, whilst others would remain +unexplored. But the system of reproduction +does not consist merely of a search for the +breeding ground, and of the discharge of the +sexual function; it is a much more complex +business, yet withal more complete. Nothing +is left to chance; the end is attained step by +step; and each successive stage marks the +appearance of some specific factor which contributes +towards the success of the whole. We +start with the appropriate organic condition +under which, when adequate stimulation is +provided, the disposition to secure a territory +comes into functional activity. Within the +field of this disposition we can distinguish +certain specific impulses. In sequential order +we have the impulse to seek the breeding +ground; the appropriate situation which gives +rise to an impulse to dwell in it; and the act +of establishment which supplies the condition +under which the impulse to drive away intruders +is rendered susceptible to stimulation. Grouping +these impulses, for the convenience of treatment, +under one general heading, I speak of +an impulse to seek isolation. It implies some +kind of action with some kind of change as +its correlated effect; and from it there flows<span class='pagenum'><a name="Page_281" id="Page_281">281</a></span> +a ceaseless energy directed towards a definite +end which for us, who can perceive its prospective +value, is isolation in an appropriate environment. +The emphasis here is on "isolation," for it +involves competition, and there cannot be competition +without some change in the relative +positions occupied by different individuals; so +that in each recurring season there will be +not only a re-arrangement of ground formerly +occupied but an arrangement of ground formerly +deserted.</p> + +<p>(2) That the older birds return to the +locality wherein they had formerly reared +offspring, and the younger to the neighbourhood +of their birthplace, was always deemed +probable. But in recent years evidence which +cannot be rebutted has been supplied by the +marking of birds. This evidence, details of +which can be found in the summary of results +published annually by Mr. Witherby in <i>British +Birds</i>, demonstrates that the adult frequently +returns not only to the same locality in which +it formerly bred, but even to the same station; +that it does so year after year; that this mode +of behaviour is not peculiar to one sex; and +that many of the young breed in the locality +in which they were reared. Such being well-established +facts, we can infer the existence of +an innate ability to revisit the place wherein +the enjoyment of breeding, or of birth, had +formerly been experienced. Of its nature we +know little or nothing. It would almost seem +as if there must be some recollection of past<span class='pagenum'><a name="Page_282" id="Page_282">282</a></span> +enjoyment, but all that can be definitely asserted +is—that past experience somehow becomes +ingrained in the life of the individual and +determines present behaviour. What, however, +is of importance to us at the moment is not the +<i>ad hoc</i> nature of the bird, but the biological +consequences to which the behaviour leads. +For if, on the average, individuals return to +their former haunts, it follows that the annual +dispersion will not be merely a repetition in this +season of that which had occurred in a previous +one, but that the little added this year will +become the basis for further additions in the +next. The innate ability is handed down from +generation to generation, and, in so far as it +contributes to success, is fostered and developed +by selection; and the modifications of behaviour +to which it leads, since the results of prior +process in the parent persist as the basis and +starting-point of subsequent process in the +offspring may in a sense also be said to be +handed down.</p> + +<p>(3) The conditions in the external world may +be organic or inorganic. By organic I mean +the conditions which depend upon the number +of competitors or enemies by which a bird is +surrounded. The competitors may include other +species which require a similar environment; and +the enemies, species which prey upon it, or +animals which take its young or its eggs. They +vary in different seasons, in different districts, +and in nature and extent—the success of one +species leads to the failure of another, and the<span class='pagenum'><a name="Page_283" id="Page_283">283</a></span> +multiplication of the Jay or of the Magpie +robs us of many a songster.</p> + +<p>By inorganic I refer to the changes in the +climate and in the surface of the earth. The +nourishment of the young depends upon a +regular supply of food, and the supply of food +depends upon the climate which alters in +different periods; in one decade the temperature +falls below, whilst in another it rises above, +the normal, and, as the insect life fluctuates, +so there is fluctuation in the bird population. +The changes in the surface of the earth are +manifold. Little by little the alder (<i>Alnus +glutinosa</i>) overspreads the marsh. Young +shoots spring up here and there, in a few +years grow into bushes, and in a few more +years are trees; and the dense masses of rush +which seemed to choke their growth, yielding +their position of importance, slowly disappear. +And where formerly the <i>Orchis latifolia</i>, <i>Orchis +mascula</i>, and <i>Juncus communis</i> grew in mingled +confusion, nothing but water, moss, and the +spreading roots of alder cover the ground. +As the rush disappears, many birds that for +generations have inhabited that marsh must +seek accommodation elsewhere. Ancient breeding +haunts thus disappear, new ones come into +being, and even those which appear to be +permanent are almost imperceptibly changing.</p> + +<p>Now the bird inherits a nervous system, +which works under internal excitation and +external stimulation. Given the appropriate +organic condition and adequate stimulation,<span class='pagenum'><a name="Page_284" id="Page_284">284</a></span> +and the impulse to seek isolation comes into +functional activity. What the organic condition +is and how it arises we do not exactly know; +all we know is that organic changes do take +place in the breeding season, that these changes +profoundly modify character, and that they +correspond with the seasonal growth of the +sexual organs. And with regard to the question +of stimulation, we have again to confess to +much ignorance, although certain facts are presented +to observation which seem to indicate +the direction in which the stimulus lies. For +example, it is well known that abnormal climatic +conditions influence behaviour; we see migrants +retracing their flight along the very course they +travelled a short time previously—driven headlong +by the blizzard, that at least is what we +say. But if the wind, instead of being cold and +from the north, is warm and from the west, do +they retrace their flight? I have not found it +so. And if there be no wind and the temperature +is low, are they still affected? Again, I +have not found it so. When, as we commonly +say, they fly before the storm, some change +takes place in their organic complex, some new +impulse receives stimulation or the former one +lacks it. If, after Lapwings have established +themselves in their territories, the weather +becomes exceptionally severe, the birds collect +together again in flocks and revert to their +winter routine; and under similar circumstances, +Buntings fail to sing and temporarily desert +their territories. In such cases it is clear that<span class='pagenum'><a name="Page_285" id="Page_285">285</a></span> +the impulse to seek isolation ceases for a time +to dominate the situation. The inference, therefore, +is that atmospheric changes bear some +relation to the functioning of the instinct; but +whether it be temperature, or humidity, or the +direction and velocity of the wind, or a combination +of two or more of these factors that supplies +the stimulus, we cannot tell.</p> + +<p>The appropriate organic condition and the +stimulus have then still to be determined, and +we must pursue our inquiry from the point at +which the impulse comes into functional activity. +We will take a simple case, and one free from +complication.</p> + +<p>Let us suppose that there is an area bereft +of bird life, if it can be so imagined, but in +proximity to other inhabited areas. Into this +area, whilst in search of isolation, let us imagine +that a Yellow Bunting finds its way. After the +manner of its race it establishes a territory and +occupies, let us say at a low computation, half an +acre of ground. It then obtains a mate, breeds, +and rears offspring, two of which we will assume +are males. Reproduction ended, the birds desert +the area, and in the following spring, when the +impulse again asserts itself, parents and offspring +seek again their former haunts. We now have +three males, each of which occupies half an acre, +and each of which rears two offspring—that is the +position at the close of the second year. In the +third year the number will have increased to +nine and the area occupied to 4½ acres; and so +on in succeeding years, until by the beginning of<span class='pagenum'><a name="Page_286" id="Page_286">286</a></span> +the eleventh year, we have 59,048 Yellow +Buntings occupying 29,524½ acres or 46 square +miles. This, then, will be the result of the +operation of the impulse, providing that all the +individuals survive and that no complications +supervene.</p> + +<p>But of course complications are numerous, +some of which retard while others accelerate the +rate of expansion. These complications arise +from various sources—in the first place from +natural enemies which prey upon the birds or +upon their eggs; in the next place from climate +which, if it happens to be unfavourable, may +mean that food is scarce and that only a small +percentage of the young survive; and lastly +from rivals—and by rivals I mean closely related +forms that require a similar station and similar +food—which, by occupying available ground, +may check expansion, or, by forcing a continuation +of the search, may widen it.</p> + +<p>Now when individuals fail as many do fail +in their initial attempt to secure territory, the +activity of the impulse still persists, and there is +no control over the direction in which the bird +continues to wander whilst in search of its end. +Some therefore seek in this direction, others in +that; some wander inwards into inhabited areas +and fail to find accommodation, or, according to +the relative strength of their impulse, perhaps +succeed and so set free a new competitor, +others wander outwards into country uninhabited +by the species. These latter we will +call "pioneers." They may find accommoda<span class='pagenum'><a name="Page_287" id="Page_287">287</a></span>tion +within a comparatively short distance of +their base, or they may come into competition +with rivals and fail, not necessarily on account +of any congenital weakness of ability, but +because being warned by an alien song, they +may be precluded from coming into contact +with just the environing conditions which can +supply the stimulus and allow behaviour to run +its further course—and so be obliged to extend +their search into remoter districts. But it must +not be overlooked that they will be placed in a +most advantageous position so far as the attainment +of reproduction is concerned. In their +search for territory they will meet with little +opposition and will be free to select whatsoever +ground they will; and be free also from +intrusion by neighbouring males, which is so +frequent in occurrence and continues for so +long in congested areas. Moreover, in thinly +populated districts, the pressure upon the +available means of support will not be so +great, neither will natural enemies be so plentiful; +and since the offspring, guided by prior +experience, return to the neighbourhood of +their birthplace, the advantages thus gained +will be shared by the succeeding generation. +It follows, then, that the range of a species +will not always be continuous, will not, that +is to say, proceed by a series of successive +steps, but that sometimes in this direction and +at other times in that, the chain of territories +will be interrupted and different individuals +separated by distances of greater or lesser<span class='pagenum'><a name="Page_288" id="Page_288">288</a></span> +extent. New colonies will thus come into +being; and as the unlimited increase of the +population over limited areas gradually reintroduces +into them the struggle for territory, new +centres of distribution, where the process will +repeat itself and from which expansion will +proceed afresh, will be formed. Hence, though +it is clearly impossible for the progeny of one +pair of Yellow Buntings to overspread the whole +of the 46 square miles, it is by no means impossible +for the limits of their range to exceed even +those limits within the eleven years.</p> + +<p>To sum up our knowledge regarding this +phase. Of the organic condition which renders +the impulse responsive to stimulation we know +very little; and though certain facts of observation +seem to indicate the direction in which the +stimulus is to be found, we must here again +confess to much ignorance. So far as can be +seen, however, the impulse to seek isolation +with its correlative territory, leads to constant +modification in the breeding range of most +species. The occupation of the small space of +ground which each individual requires, the +extent of which has been gradually adjusted to +suit the needs of different species, results in +expansion not only in one direction but in every +direction, and not only in one season but in every +season. And if there were no complications in +the external world this expansion would proceed, +as we have seen, with astonishing rapidity. But +complications, some of which are favourable and +others unfavourable, are numerous, and it is<span class='pagenum'><a name="Page_289" id="Page_289">289</a></span> +difficult to estimate their importance or to +indicate their precise effect; the former, however, +accelerate the rate of expansion, whilst the +latter retard it. Those individuals that wander +outwards and seek territory on the outskirts of +the range we have called "pioneers." They will +have advantages over others that, wandering +inwards, seek isolation in congested districts, +and will succeed where the latter fail; and since +there is in the young an innate ability to +return to the district wherein they were reared, +the advantages so gained may be said to be +handed on from generation to generation.</p> + +<p>Let us now turn to the contra-phase, and +endeavour to ascertain whether the gregarious +instinct bears any relation to the seasonal +desertion of the breeding ground. The conclusion +at which we have already arrived regarding +this instinct is that it forms part of the inherited +nature of most species; that its functioning is +suppressed when a bird is actually in occupation +of a territory; and that it is serviceable in promoting +the welfare of the individual. We +cannot of course observe the instinct. What +we observe, when reproduction is ended, is a +change in the relations of different individuals; +instead of arousing mutual hostility, they attract +one another, from which we infer the existence +of something which determines their conduct, +and this "something" we speak of as an +instinct.</p> + +<p>To what does this change lead? Let us +suppose that there is an area inhabited by one<span class='pagenum'><a name="Page_290" id="Page_290">290</a></span> +species; that the number of inhabitants has +reached the maximum that the means of +sustenance will allow; and that the season +of reproduction is drawing to a close. The +position will then be as follows. All the +available breeding ground is divided into territories; +each territory is occupied by one unit, +the family, and each individual is able to fend +for itself; changes both internal and external +begin to take place, the gregarious instinct +comes into functional operation, and the supply +of food diminishes—that roughly is the position. +The internal factor operates so that the sight +of this individual or the call of that, instead of +evoking hostility as heretofore and keeping +different units apart, proves now an irresistible +attraction; so that in place of a number of +individuals evenly dispersed over the whole of +this area, a small number of flocks of various +dimensions are stationed at certain points, which +points are determined partly by experience, +partly by the supply of food, and partly by +accident. This implies for each individual some +movement in some direction. But since the +population of this imaginary area has reached +the maximum, and the supply of food, though +limited in distribution, is nevertheless plentiful, +such movements will be irregular and will proceed +in no definite direction.</p> + +<p>Now let us suppose that the breeding range +extends and that fresh ground is occupied by +pioneers. When reproduction and the rearing +of broods are ended and the gregarious instinct<span class='pagenum'><a name="Page_291" id="Page_291">291</a></span> +becomes dominant, these pioneers, or at least +some of them, will revisit the area wherein +formerly they associated with companions. +Their offspring, however, though they will +have the inherited impulse and the innate +tendency, will not have the experience; how +then will they behave? There can be no doubt +that some will accompany the older birds, and, +being led by them, will share the experience of +a former generation; nor any question that +others will collect together in the neighbourhood +of their birthplace and, if their impulse is +satisfied, will remain there so long as food is to +be found. Thus the gregarious instinct, working +in close relation with acquired experience, +will on the one hand lead to the formation of +organised movements in certain directions, +whilst on the other it will lead to the formation +of new areas of association which will follow in +the wake of the expansion.</p> + +<p>We have assumed, in the imaginary case +which we have just taken, that the conditions +in the external world are such as enable the +birds to endure throughout the year—in short, +that there are no complications regarding the +supply of food. But we must bear in mind +that so long as conditions are favourable during +the period of reproduction, which is of short +duration, the breeding range can continue to +expand, and that therefore, in the course of +centuries, regions will come to be occupied +wherein, owing to alternations of climate or +physical changes in the surface of the earth,<span class='pagenum'><a name="Page_292" id="Page_292">292</a></span> +food will be impossible, or at any rate difficult +to obtain at certain seasons. Hence there will +come a time when the area of association ceases +to follow in the wake of the expansion, and +the breeding area begins to diverge from the +subsistence area.</p> + +<p>How, then, is the gulf between these two +areas to be bridged? We can of course say +that those individuals which, in virtue of some +slight variation of hereditary tendency, return +to regions where food is plentiful will survive; +whilst others, less well endowed, will perish. +We can state the position in some such general +terms, and doubtless there would be truth in +the statement, but it does not carry us far; +we wish to know more of the nature of the +tendency, and of the manner in which it has +evolved. Well now, in this new situation +which arises, two things are apparent—that +the struggle for existence becomes a struggle +for the means of subsistence, and that anything +in the inherited constitution of the bird which +can be organised to subserve the biological end +in view becomes of selection value. So long as +food can always be procured in the new areas of +association, the individuals that behave in +accordance with ancestral routine gain thereby +no particular advantage; but directly the +breeding range extends into regions where +the supply fluctuates, traditional experience +becomes a factor in survival, and those individuals +that come under its influence will, on +the average, be more likely to endure and so<span class='pagenum'><a name="Page_293" id="Page_293">293</a></span> +to procreate their kind and maintain the +tradition. Let it once be granted that there +is an innate capacity to retain in later phases +of routine the experience gained in earlier +phases, and it is difficult to see how traditional +guidance can be refused recognition as a factor +in the developing situation. But only <i>a</i> factor, +and by no means the most important one; for +observation has shown that the young are +capable of performing the return journey +without guidance. Something therefore <i>is</i> +inherited, some impulse which comes into +functional activity at a specified time, and leads +the bird to set forth in a given direction.</p> + +<p>There are no grounds for supposing that +the experience of one generation forms any +part of the hereditary equipment of subsequent +generations. In what direction then are we to +look for the congenital factor? What is given +is an inherited tendency to co-operation and +mutual help, and an innate capacity to make +use of the results of experience. The inherited +tendency, as we have seen, leads on the one +hand to the formation of new areas of association, +whilst on the other, since it is the means +of bringing isolated individuals into contact, +it leads to experience being handed on from +generation to generation, which, in its turn, +results in a certain amount of backward movement +along the line of expansion. It forms +part of the hereditary equipment of many +species, and is serviceable in promoting the +welfare of the individual. Moreover, there is<span class='pagenum'><a name="Page_294" id="Page_294">294</a></span> +reason to believe that its origin dates back to +an early period in the evolution of the higher +forms of life; and if in the subsequent course +of evolution it could have been so organised +as to serve a double purpose, so much the more +reason would there have been for its survival. +In what does the instinct consist? Is it merely +that the sight of this individual or the call of +that proves at some particular moment an +irresistible attraction, or does the appropriate +organic condition give rise, as is generally +supposed, to some preceding state of uneasiness? +In the former case, the temporarily isolated +individual or colony would have but little +chance of sharing in the benefits which mutual +association confers upon the associates; in the +latter, the feeling of discomfort would lead to +restlessness, and would thus bring the bird into +touch with the environing circumstances under +which instinctive behaviour could run its +further course. So that it is probable that the +movements of each individual, prior to its +becoming a unit in the flock, are not accidental +but are determined in some measure by racial +preparation.</p> + +<p>Now if the fundamental assumption of the +doctrine of the struggle for existence be true, +the gregarious instinct will not be quite alike in +all the members of different broods, nor even in +each member of the same brood; that is, +variation will occur in all possible directions. +And we shall not, I think, exceed the limits of +probability if we assume that different individuals<span class='pagenum'><a name="Page_295" id="Page_295">295</a></span> +vary in the persistency with which they strive +to attain their unknown end, and in the direction +in which they travel in pursuit of it. So that in +each generation they will fall into three classes: +(1) those which are inert, (2) those which +wander along the line of expansion, (3) those +which wander in other directions. If then the +struggle for life at this particular juncture in the +evolution of the breeding range is a struggle for +the means of subsistence, the members of these +three classes will not be in a like satisfactory +position so far as the competition for food is +concerned. Those in the first class—<i>i.e.</i>, those +in which the activity feelings are weak—will +neither gain the benefits which arise from +mutual help, nor will they have much prospect +of enduring through the season of scarcity. +Those in the third class will, it is true, derive +some assistance one from another, and so be in +a better position to discover what food may be +available; but inasmuch as they will remain in +regions where the climate alternates and the +supply of food is liable to fall below the +minimum required, the chances are that a high +percentage will fail in the struggle for existence. +We come now to those in the second class, and +it is upon them that I wish more particularly to +focus attention. The initial movement in their +case will be in the direction from which outward +expansion has all along taken place. Within a +comparatively short distance they will reach +districts where the species is plentiful, and here, +associating with others that have some traditional<span class='pagenum'><a name="Page_296" id="Page_296">296</a></span> +experience, they will be guided by them and +will find themselves in regions where food is +plentiful. Hence in each generation those will +survive that, owing to some congenital variation +of their instinct, seek satisfaction for their +impulse in a direction which brings them under +the influence of tradition. And though at first +but slight and not in themselves of survival +value, such variations, since they coincide with +modifications of behaviour due to acquired +experience, will be preserved and in the process +of time so accumulated as to be capable of +determining the direction and extent of the +movement.</p> + +<p class="tb">But the young Cuckoo deserts this country +many weeks after its parents, and there is no +reason to suppose that it lives in society when +eventually its destination is reached; and the +young Falcon passes to the south, and is +certainly not gregarious—how then can we +explain their behaviour in terms of something +which they show no signs of possessing? I do +not wish to make light of a difficulty which +admittedly, at first sight, is a grave objection to +the view that the gregarious instinct has been +operative in the manner here claimed for it. It +must, however, be borne in mind that this +instinct, though originally developed to serve +the purpose of mutual protection, supplies the +material upon which evolution works when the +extension of the breeding range creates a +situation requiring readjustment on the part of +the organism to new conditions of life; and that<span class='pagenum'><a name="Page_297" id="Page_297">297</a></span> +those variations which can be so modified as to +be in useful relation to the new environmental +circumstances are seized upon by natural selection +and, being transmitted, form the foundation of +a specific inherited response, no longer dependent +upon, though operating in close relation with +the primitive response whence originally it +sprang. Thus the primordial instinct becomes +so organised as to serve a secondary purpose, +that of rendering secure a means of access to +a certain food supply. In the course of evolution +species were bound to arise which, owing +to some peculiar conditions, derived greater +advantage from living solitary than from living +in society. Does it then follow, because such +species manifest no inclination to live in society, +that the instinct never has played any part in +their lives? Or because the primary purpose +has lapsed, does it follow that the secondary +no longer exists?</p> + +<p>Let me recapitulate the principal considerations +which I have discussed in this chapter.</p> + +<p>Though I have been advancing a theory, and +though I have taken much for granted, yet it +will, I think, be admitted that both the theory +and what has been taken for granted rest on +observational grounds. As our starting-point +we have a bird whose inherited nature alternates +according to the season, and in whose nature we +can distinguish two contra-phases—the one to +live in society, the other to live solitary. While +both have their part to play in furthering the<span class='pagenum'><a name="Page_298" id="Page_298">298</a></span> +life of the individual, for biological interpretation +there is only one end, the prospective value of +which is the continuance of the race. We may +say that the latter phase is the more important +of the two because it is directly concerned with +reproduction. But we shall make a great mistake +if we attach peculiar importance to one +phase, or to one mode of behaviour within that +phase, or to one action within that mode of +behaviour; for if there is one thing certain it is +that the whole is an inter-related whole in which +each part depends for its success upon that +which precedes it.</p> + +<p>In that phase in which the territory is the +central feature of the situation, the struggle +for existence is in operation in its acutest form; +all the congenital and acquired capacities of the +bird—pugnacity, song, capacity to utilise in +later phases the experience gained in prior +phases, all these are organised to subserve an +end—a proximate end—which in its simplest +terms may be described as "isolation." Isolation +is then the first step in the process of reproduction, +and any individual that fails to make it +good, fails to procreate its kind. But isolation +implies separation, and the degree of separation +varies in different species, from the few square +feet of cliff required by the Guillemot to the +few square miles of barren moor over which the +Peregrine exercises dominion. One species must +occupy sufficient ground to enable it to secure +food for its young; another requires sufficient, +but no more, upon which to deposit its egg; and<span class='pagenum'><a name="Page_299" id="Page_299">299</a></span> +a third must secure a position for its nest within +the community. Hence it follows that the +degree of separation varies with the conditions +of existence. Since, however, the conditions in +the external world are constantly changing +according to the relative abundance or scarcity +of enemies, the rise or fall of rivals, the physical +changes in the earth's surface, and the alterations +of climate, it is clear that isolation can only be +obtained with difficulty, and that the competition +for it must be severe. Some individuals +therefore fail to breed, whilst others, perhaps +because their impulse is stronger, persevere +and seek stations elsewhere. What are their +prospects of finding them? By extending the +field of their activities, they will wander into +districts remote from the scene of competition, +districts where not only food is plentiful but +where enemies and rivals are scarce; and to +these pioneers, if to any, success in reproduction +will most certainly be assured. But not only is +it they who will benefit; their offspring also, +when the time comes for them to take their part +in the maintenance of the race, will share in the +success of their parents, for even though they +may not escape competition from individuals of +closely related forms, they will meet with but +little from those of their own kind. Now +species which live throughout the year in the +vicinity of their territory are comparatively few, +the majority are obliged to wander in search +of food so soon as reproduction is ended, and +their behaviour is determined not only by its<span class='pagenum'><a name="Page_300" id="Page_300">300</a></span> +abundance or scarcity, but also by the powerful +gregarious impulse which waxes in proportion +as the instincts connected with reproduction +wane. If, then, when the sexual instinct again +becomes predominant, the experience of the +former season nowise affects their movements, +little or no progress will be made in the expansion +of the range. But just as a certain entrance +into the bush and pathway through it, when +once made use of in the process of building, +becomes so firmly established as to form the +sole highway to and from the nest, so likewise, +when the impulse to seek isolation repeats +itself, the bird is constrained to seek the +neighbourhood wherein it had experienced the +enjoyment of breeding or of birth. Thus the +little that is added one year becomes the basis +for further additions in the next, and new +centres of distribution are continually being +formed from which expansion proceeds anew.</p> + +<p>Now as the range gradually extends into +regions where the climate alternates and food at +certain seasons is consequently scarce, the +distance between the customary area of association +and that of reproduction must perforce +widen. The question then arises: How will the +young that have no experience find their way to +regions wherein they can endure? The forces +which may have been organised to subserve the +end in view are three: (1) Acquired experience, +(2) tradition, (3) the gregarious instinct. The +pioneer that carries the range a little further +forward starts from a base where it has associated<span class='pagenum'><a name="Page_301" id="Page_301">301</a></span> +with companions and found food plentiful; and +when the impulse to live in society again asserts +itself, it not only repeats its former experience +but hands on the habit thus acquired to those of +the next generation that happen to accompany +it. Granting, however, that by successive +increments in the distance traversed, traditional +guidance may in time accomplish much, it +cannot account for all the known facts, it +cannot at any rate explain the fact that in some +cases the inexperienced offspring finds its way +to the food area without guidance. Something, +therefore, <i>is</i> inherited. And my suggestion is +this: That the gregarious instinct, the ancient +origin of which we can infer from its manifestation +in so many and diverse forms of life, +supplies the material upon which evolution +works; that variations of the initial impulse, at +first slight and not in themselves of selection +value, in so far as they coincide in direction with +modifications of procedure due to experience or +tradition, are preserved; and that, in the process +of time, they are so accumulated as to form +a specific congenital endowment determining +a definite mode of behaviour.</p> + +<hr /> + +<h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_1_1" id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">1</span></a> June 1915, R. M. Barrington.</p></div> + +<div class="footnote"><p><a name="Footnote_2_2" id="Footnote_2_2"></a><a href="#FNanchor_2_2"><span class="label">2</span></a> <i>Dictionary of Birds</i>, p. 556.</p></div> + +<div class="footnote"><p><a name="Footnote_3_3" id="Footnote_3_3"></a><a href="#FNanchor_3_3"><span class="label">3</span></a> <i>Social Psychology.</i></p></div> + +<div class="footnote"><p><a name="Footnote_4_4" id="Footnote_4_4"></a><a href="#FNanchor_4_4"><span class="label">4</span></a> <i>Manual of Psychology.</i></p></div> + +<div class="footnote"><p><a name="Footnote_5_5" id="Footnote_5_5"></a><a href="#FNanchor_5_5"><span class="label">5</span></a> <i>Ibis</i>, April 1918.</p></div> + +<div class="footnote"><p><a name="Footnote_6_6" id="Footnote_6_6"></a><a href="#FNanchor_6_6"><span class="label">6</span></a> <i>Zoologist</i>, 1912, p. 327.</p></div> + +<hr /> +<p><span class='pagenum'><a name="Page_302" id="Page_302">302</a></span></p> + +<h3>INDEX<br /><br /></h3> +<ul class="IX"><li> +Acquired experience, <a href="#Page_300">300</a> +</li><li> +Adjustments, transitory, of distribution, <a href="#Page_275">275</a> +</li><li> +Alarm notes, <a href="#Page_119">119</a> +</li><li> +Arrival, advantages and disadvantages of late, <a href="#Page_33">33</a>-44 +</li><li> +Assemblies in winter, <a href="#Page_262">262</a>, <a href="#Page_263">263</a> +</li><li> +Assembly grounds, <a href="#Page_173">173</a> +</li><li> +Attainment of reproduction, <a href="#Page_171">171</a> +</li><li> +</li><li> +<span class="smcap">Barrington, R. M.</span>, on the sex of migrants, <a href="#Page_25">25</a> +</li><li> +Battle between two male Cuckoos, <a href="#Page_82">82</a> +</li><li> +—— between two Moor-Hens, <a href="#Page_86">86</a>, <a href="#Page_92">92</a>, <a href="#Page_93">93</a>, <a href="#Page_94">94</a> +</li><li> +—— —— Pied Wagtails, <a href="#Page_86">86</a> +</li><li> +—— —— Raven and Buzzard, <a href="#Page_217">217</a> +</li><li> +—— —— Raven and Peregrine, <a href="#Page_216">216</a> +<span style="margin-left: 1em;">law of, <a href="#Page_13">13</a>,19</span> +</li><li> +Behaviour routine, <a href="#Page_262">262</a> +</li><li> +—— sexual, <a href="#Page_3">3</a> +</li><li> +Bickerings, <a href="#Page_96">96</a> +</li><li> +Birthplace, return to, <a href="#Page_43">43</a>, <a href="#Page_50">50</a> +</li><li> +Blackbird, <a href="#Page_87">87</a>, <a href="#Page_182">182</a>, <a href="#Page_222">222</a>, <a href="#Page_244">244</a> +</li><li> +Blackcap, <a href="#Page_81">81</a>, <a href="#Page_156">156</a>, <a href="#Page_224">224</a>, <a href="#Page_230">230</a> +</li><li> +Black Grouse, <a href="#Page_63">63</a> +</li><li> +Black-tailed Godwit, <a href="#Page_53">53</a> +</li><li> +Boundaries, <a href="#Page_1">1</a>, <a href="#Page_5">5</a> +</li><li> +—— conflicts for retention of, <a href="#Page_7">7</a>, <a href="#Page_62">62</a> +</li><li> +—— disputes as to, <a href="#Page_1">1</a> +</li><li> +Brambling, <a href="#Page_124">124</a> +</li><li> +Breeding ground, search for appropriate, <a href="#Page_270">270</a>, <a href="#Page_271">271</a> +</li><li> +—— range, extension of, <a href="#Page_291">291</a>-92 +</li><li> +—— site, acquirement of, <a href="#Page_3">3</a> +</li><li> +—— stations, evolution of, <a href="#Page_15">15</a>-19 +</li><li> +—— —— repeatedly visited long before nesting-time, <a href="#Page_64">64</a> +</li><li> +—— territory, <a href="#Page_2">2</a>, <a href="#Page_3">3</a>, <a href="#Page_7">7</a> +</li><li> +—— —— evolution of, <a href="#Page_18">18</a> +</li><li> +—— —— foundation of, <a href="#Page_7">7</a> +</li><li> +—— —— innate capacity to return to former, <a href="#Page_279">279</a>-81 +</li><li> +Bridled Guillemot, <a href="#Page_64">64</a> +</li><li> +Brooding, <a href="#Page_180">180</a> +</li><li> +—— impulse, <a href="#Page_191">191</a> +</li><li> +Bunting, Cirl, <a href="#Page_28">28</a>, <a href="#Page_140">140</a> +</li><li> +—— Corn, <a href="#Page_28">28</a> +</li><li> +—— Reed, <a href="#Page_28">28</a>, <a href="#Page_68">68</a>, <a href="#Page_69">69</a>, <a href="#Page_85">85</a>, <a href="#Page_104">104</a>, <a href="#Page_132">132</a>, <a href="#Page_158">158</a>, <a href="#Page_160">160</a>, <a href="#Page_244">244</a> +</li><li> +—— Yellow, <a href="#Page_28">28</a>, <a href="#Page_30">30</a>, <a href="#Page_47">47</a>, <a href="#Page_64">64</a>, <a href="#Page_140">140</a>, <a href="#Page_159">159</a>, <a href="#Page_162">162</a>, <a href="#Page_183">183</a>, <a href="#Page_187">187</a>, <a href="#Page_188">188</a>, <a href="#Page_189">189</a>, <a href="#Page_235">235</a>, <a href="#Page_236">236</a>, +<a href="#Page_286">286</a> +</li><li> +Buzzard, <a href="#Page_217">217</a> +</li><li> +</li><li> +<span class="smcap">Capacity,</span> innate, to return to former breeding territory, <a href="#Page_279">279</a>-81 +</li><li> +Carrion Crow, <a href="#Page_226">226</a> +</li><li> +Chaffinch, <a href="#Page_28">28</a>, <a href="#Page_31">31</a>, <a href="#Page_32">32</a>, <a href="#Page_33">33</a>, <a href="#Page_45">45</a>, <a href="#Page_87">87</a>, <a href="#Page_103">103</a>, <a href="#Page_156">156</a>, <a href="#Page_159">159</a>, <a href="#Page_235">235</a>, <a href="#Page_236">236</a>, <a href="#Page_244">244</a> +</li><li> +—— Donegal, <a href="#Page_160">160</a> +<span class='pagenum'><a name="Page_303" id="Page_303">303</a></span> +Change of breeding quarters owing to unsuitableness, <a href="#Page_50">50</a> +</li><li> +Chiffchaff, <a href="#Page_49">49</a>, <a href="#Page_51">51</a>, <a href="#Page_80">80</a>, <a href="#Page_139">139</a>, <a href="#Page_140">140</a>, <a href="#Page_221">221</a>, <a href="#Page_224">224</a>, <a href="#Page_244">244</a> +</li><li> +Cirl Bunting, <a href="#Page_28">28</a>, <a href="#Page_140">140</a> +</li><li> +Clarke, W. Eagle, <i>Studies in Bird Migration</i>, <a href="#Page_24">24</a> +</li><li> +Cleanliness of nest, <a href="#Page_180">180</a> +</li><li> +Cliff-breeding species, <a href="#Page_63">63</a> +</li><li> +Climatic changes, alteration of routine, due to, <a href="#Page_284">284</a> +</li><li> +—— changes, food dependent on, <a href="#Page_283">283</a> +</li><li> +—— conditions, influence of, <a href="#Page_20">20</a> +</li><li> +Communities, <a href="#Page_202">202</a> +</li><li> +—— birds after breeding-season remain in, <a href="#Page_265">265</a>-67 +</li><li> +Competition, female, for males, <a href="#Page_13">13</a> +</li><li> +Complexity of strife, <a href="#Page_84">84</a>-85 +</li><li> +Conflicts between males during the mating period, <a href="#Page_74">74</a>, <a href="#Page_86">86</a> +</li><li> +—— between males during the nesting period, <a href="#Page_87">87</a> +</li><li> +—— for areas, <a href="#Page_10">10</a>, <a href="#Page_11">11</a>, <a href="#Page_13">13</a>, <a href="#Page_62">62</a> +</li><li> +—— of Ruff, <a href="#Page_54">54</a> +</li><li> +—— sexual, <a href="#Page_10">10</a> +</li><li> +Congenital disposition, <a href="#Page_135">135</a> +</li><li> +Contests between males for possession of females, <a href="#Page_80">80</a> +</li><li> +Coot, <a href="#Page_61">61</a> +</li><li> +Corn-Bunting, <a href="#Page_28">28</a> +</li><li> +Corncrake, <a href="#Page_39">39</a> +</li><li> +Crow, Carrion, <a href="#Page_226">226</a>, <a href="#Page_227">227</a> +</li><li> +Crow, Hooded, <a href="#Page_202">202</a> +</li><li> +Cuckoo, <a href="#Page_52">52</a>, <a href="#Page_82">82</a>, <a href="#Page_144">144</a>, <a href="#Page_296">296</a> +</li><li> +—— restricted breeding area, <a href="#Page_52">52</a> +</li><li> +Curlew, <a href="#Page_119">119</a>, <a href="#Page_138">138</a>, <a href="#Page_140">140</a>, <a href="#Page_250">250</a>, <a href="#Page_262">262</a>, <a href="#Page_263">263</a>, <a href="#Page_265">265</a>, <a href="#Page_273">273</a> +</li><li> +</li><li> +<span class="smcap">Danger</span> warnings, <a href="#Page_269">269</a> +</li><li> +Darwin, C., <i>Descent of Man</i>, <a href="#Page_35">35</a> +</li><li> +—— on the arrival of males before females, <a href="#Page_35">35</a> +</li><li> +Defence of territory, <a href="#Page_6">6</a> +</li><li> +Development, sexual, <a href="#Page_6">6</a> +</li><li> +Disposition, congenital, <a href="#Page_135">135</a> +</li><li> +—— functioning of, <a href="#Page_74">74</a> +</li><li> +—— inherited, <a href="#Page_5">5</a> +</li><li> +—— to defend the territory, <a href="#Page_73">73</a>-118 +</li><li> +—— to mate, <a href="#Page_27">27</a> +</li><li> +—— to remain in a particular place in a particular environment, <a href="#Page_6">6</a> +</li><li> +—— to secure a territory, <a href="#Page_6">6</a>, <a href="#Page_20">20</a>-72 +</li><li> +Distribution, adjustment of, <a href="#Page_275">275</a> +</li><li> +Dove, Turtle, <a href="#Page_126">126</a>, <a href="#Page_232">232</a> +</li><li> +Dunlin, <a href="#Page_250">250</a> +</li><li> +</li><li> +<span class="smcap">Emotional</span> behaviour, <a href="#Page_53">53</a>, <a href="#Page_82">82</a>, <a href="#Page_114">114</a> +</li><li> +—— manifestation, <a href="#Page_90">90</a>, <a href="#Page_283">283</a> +</li><li> +—— response, <a href="#Page_26">26</a> +</li><li> +Enemies, <a href="#Page_282">282</a> +</li><li> +Energy, waste of, <a href="#Page_219">219</a> +</li><li> +Environment, <a href="#Page_6">6</a> +</li><li> +—— and food, <a href="#Page_56">56</a> +</li><li> +—— changes of, <a href="#Page_283">283</a> +</li><li> +—— external, conditions in, <a href="#Page_279">279</a>, <a href="#Page_282">282</a> +</li><li> +Equipment, hereditary, <a href="#Page_6">6</a> +</li><li> +Evolution of breeding stations or territory, <a href="#Page_15">15</a>, <a href="#Page_19">19</a> +</li><li> +—— of the territory, <a href="#Page_176">176</a> +</li><li> +—— of the voice, <a href="#Page_163">163</a> +</li><li> +Existence, struggle for, <a href="#Page_294">294</a> +</li><li> +Experience, acquired, <a href="#Page_300">300</a> +</li><li> +Experiments, removal of nests for, <a href="#Page_181">181</a>, <a href="#Page_185">185</a>, <a href="#Page_190">190</a>, <a href="#Page_213">213</a>, <a href="#Page_214">214</a> +</li><li> +Exposure, its effect on nestlings, <a href="#Page_180">180</a> +</li><li> +External environment, conditions in, <a href="#Page_279">279</a>, <a href="#Page_282">282</a> +</li><li> +</li><li> +<span class="smcap">Falcon,</span> <a href="#Page_48">48</a>, <a href="#Page_71">71</a> +</li><li> +Feeding grounds, neutral, 125 in communities, <a href="#Page_70">70</a> +<span class='pagenum'><a name="Page_304" id="Page_304">304</a></span> +Females, fighting amongst, <a href="#Page_109">109</a>-118 +</li><li> +—— sexual impulse of, <a href="#Page_13">13</a> +</li><li> +Fieldfare, <a href="#Page_124">124</a> +</li><li> +Fighting instinct, <a href="#Page_79">79</a>, <a href="#Page_82">82</a> +</li><li> +Flight, emotional behaviour of Godwit during, <a href="#Page_53">53</a> +</li><li> +Flocks, in winter, birds collect together in, <a href="#Page_262">262</a> +</li><li> +Flycatcher, <a href="#Page_244">244</a> +</li><li> +Food, procuring of, <a href="#Page_5">5</a> +</li><li> +—— abundance, or scarcity of, its relation to prosperity of young, <a href="#Page_15">15</a>, <a href="#Page_16">16</a> +</li><li> +—— its bearing, on the movement of flocks, <a href="#Page_262">262</a> +</li><li> +—— rearing of young dependent on rapid and regular, <a href="#Page_179">179</a>, <a href="#Page_195">195</a> +</li><li> +—— supply, proximity to, necessary for rearing young, <a href="#Page_179">179</a>, <a href="#Page_195">195</a> +</li><li> +Fortuitous mating, <a href="#Page_174">174</a> +</li><li> +Fowler, Ward, on the value of communities, Rooks, <a href="#Page_202">202</a> +</li><li> +Fulmar, <a href="#Page_121">121</a>, <a href="#Page_247">247</a> +</li><li> +Functional activity, <a href="#Page_259">259</a> +</li><li> +—— instinct of Reeve, <a href="#Page_173">173</a> +</li><li> +Functioning of the disposition, <a href="#Page_275">275</a> +</li><li> +—— of the primary dispositions, <a href="#Page_100">100</a> +</li><li> +</li><li> +<span class="smcap">Garden</span> Warbler, <a href="#Page_223">223</a>, <a href="#Page_225">225</a>, <a href="#Page_230">230</a> +</li><li> +Gätke, H., <i>Birds of Heligoland</i>, <a href="#Page_24">24</a> +</li><li> +—— on the absence of song in birds on Heligoland, <a href="#Page_124">124</a> +</li><li> +—— on the early arrival of Guillemots on Heligoland, <a href="#Page_64">64</a> +</li><li> +Godwit, emotional behaviour of, during flight, <a href="#Page_53">53</a> +</li><li> +—— Black-tailed, <a href="#Page_53">53</a> +</li><li> +Grasshopper Warbler, <a href="#Page_39">39</a>, <a href="#Page_131">131</a>, <a href="#Page_139">139</a>, <a href="#Page_153">153</a>, <a href="#Page_155">155</a>, <a href="#Page_187">187</a>, <a href="#Page_244">244</a> +</li><li> +Greenfinch, <a href="#Page_28">28</a>, <a href="#Page_33">33</a>, <a href="#Page_140">140</a>, <a href="#Page_235">235</a>, <a href="#Page_236">236</a> +</li><li> +Gregarious instinct, <a href="#Page_20">20</a>, <a href="#Page_61">61</a>, <a href="#Page_141">141</a>, +<a href="#Page_265">265</a>-66, <a href="#Page_269">269</a>, <a href="#Page_276">276</a>, <a href="#Page_289">289</a>, <a href="#Page_290">290</a>, <a href="#Page_291">291</a>, <a href="#Page_296">296</a>, <a href="#Page_300">300</a> +</li><li> +Grouse, Black, <a href="#Page_63">63</a> +</li><li> +Guillemot, Bridled, <a href="#Page_64">64</a> +</li><li> +—— Common, <a href="#Page_63">63</a>, <a href="#Page_64">64</a>, <a href="#Page_121">121</a>, <a href="#Page_192">192</a>, <a href="#Page_195">195</a>, <a href="#Page_206">206</a>, <a href="#Page_211">211</a>, <a href="#Page_247">247</a> +</li><li> +—— Ringed, <a href="#Page_64">64</a> +</li><li> +Gull, Common, <a href="#Page_119">119</a> +</li><li> +—— Herring, <a href="#Page_210">210</a>, <a href="#Page_278">278</a> +</li><li> +</li><li> +<span class="smcap">Habit</span> formation, law of, <a href="#Page_8">8</a>, <a href="#Page_62">62</a>, <a href="#Page_65">65</a>, <a href="#Page_66">66</a>, <a href="#Page_67">67</a>, <a href="#Page_205">205</a> +</li><li> +Hawfinch, <a href="#Page_28">28</a> +</li><li> +Headquarters, <a href="#Page_176">176</a>, <a href="#Page_206">206</a>, <a href="#Page_207">207</a>, <a href="#Page_274">274</a> +</li><li> +—— restricted, <a href="#Page_8">8</a>, <a href="#Page_9">9</a>, <a href="#Page_30">30</a>, <a href="#Page_50">50</a>, <a href="#Page_58">58</a>, <a href="#Page_64">64</a>, <a href="#Page_127">127</a> +</li><li> +Hedge-Sparrow, <a href="#Page_213">213</a>, <a href="#Page_221">221</a>, <a href="#Page_244">244</a> +</li><li> +Hereditary equipment, <a href="#Page_6">6</a> +</li><li> +Herring-Gull, <a href="#Page_210">210</a>, <a href="#Page_278">278</a> +</li><li> +Hooded-Crow, <a href="#Page_202">202</a> +</li><li> +Hostility and territory, relationship between, <a href="#Page_242">242</a> +</li><li> +House-Sparrow, <a href="#Page_218">218</a> +</li><li> +</li><li> +<span class="smcap">Imitation,</span> vocal, powers of, <a href="#Page_156">156</a>, <a href="#Page_157">157</a>, <a href="#Page_161">161</a> +</li><li> +Impulse, internal, <a href="#Page_279">279</a> +</li><li> +—— to brood, <a href="#Page_191">191</a> +</li><li> +Inherited disposition, <a href="#Page_5">5</a> +</li><li> +Instinct, fighting, <a href="#Page_79">79</a>-82 +</li><li> +—— gregarious, <a href="#Page_20">20</a>, <a href="#Page_61">61</a>, <a href="#Page_141">141</a>, <a href="#Page_265">265</a>, <a href="#Page_266">266</a>, <a href="#Page_269">269</a>, <a href="#Page_276">276</a>, <a href="#Page_289">289</a>, <a href="#Page_290">290</a>, <a href="#Page_291">291</a>, <a href="#Page_296">296</a>, <a href="#Page_300">300</a> +</li><li> +—— migratory, <a href="#Page_37">37</a> +</li><li> +—— of song related to establishment of territory, <a href="#Page_125">125</a> +</li><li> +—— sexual, reawakening of, <a href="#Page_4">4</a>, <a href="#Page_18">18</a> +</li><li> +Instinctive response, <a href="#Page_180">180</a> +</li><li> +Instincts susceptible to stimulation, <a href="#Page_259">259</a> +</li><li> +Internal impulse, <a href="#Page_279">279</a> +<span class='pagenum'><a name="Page_305" id="Page_305">305</a></span> +Internal stimulation, <a href="#Page_62">62</a>, <a href="#Page_123">123</a> +</li><li> +Interpretation of battles, <a href="#Page_75">75</a> +</li><li> +Intolerance of other birds, <a href="#Page_218">218</a>, <a href="#Page_219">219</a> +</li><li> +Intrusion resented, <a href="#Page_274">274</a> +</li><li> +Isolation, impulse to seek, <a href="#Page_288">288</a> +</li><li> +—— of male, <a href="#Page_12">12</a>, <a href="#Page_62">62</a>, <a href="#Page_65">65</a>, <a href="#Page_73">73</a>, <a href="#Page_81">81</a> +</li><li> +—— of male during breeding season, <a href="#Page_267">267</a>, <a href="#Page_272">272</a>, <a href="#Page_273">273</a>, <a href="#Page_275">275</a>, <a href="#Page_281">281</a> +</li><li> +</li><li> +<span class="smcap">Jay,</span> <a href="#Page_87">87</a>, <a href="#Page_156">156</a>, <a href="#Page_283">283</a> +</li><li> +</li><li> +<span class="smcap">Kestrel,</span> <a href="#Page_228">228</a> +</li><li> +Kittiwake, <a href="#Page_116">116</a>, <a href="#Page_200">200</a>, <a href="#Page_247">247</a> +</li><li> +</li><li> +<span class="smcap">Lapwing,</span> <a href="#Page_58">58</a>, <a href="#Page_59">59</a>, <a href="#Page_61">61</a>, <a href="#Page_62">62</a>, <a href="#Page_64">64</a>, <a href="#Page_84">84</a>, <a href="#Page_103">103</a>, <a href="#Page_104">104</a>, <a href="#Page_126">126</a>, <a href="#Page_189">189</a>, <a href="#Page_190">190</a>, <a href="#Page_220">220</a>, <a href="#Page_251">251</a>, <a href="#Page_284">284</a> +</li><li> +Lapwing, life-history of, <a href="#Page_58">58</a>-61 +</li><li> +Late arrival, advantages and disadvantages of, <a href="#Page_33">33</a>-44 +</li><li> +Law of battle, <a href="#Page_74">74</a>, <a href="#Page_75">75</a>, <a href="#Page_86">86</a> +</li><li> +Lesser Whitethroat, <a href="#Page_230">230</a>, <a href="#Page_244">244</a> +</li><li> +Linnet, <a href="#Page_156">156</a> +</li><li> +</li><li> +<span class="smcap">M'Dougall,</span> Dr, <i>Social Psychology</i>, <a href="#Page_77">77</a> +</li><li> +Magpie, <a href="#Page_219">219</a>, <a href="#Page_283">283</a> +</li><li> +Males arrive before advent of females, <a href="#Page_24">24</a> +</li><li> +Marsh-Warbler, <a href="#Page_39">39</a>, <a href="#Page_40">40</a>, <a href="#Page_52">52</a>, <a href="#Page_81">81</a>, <a href="#Page_132">132</a>, <a href="#Page_140">140</a>, <a href="#Page_153">153</a>, <a href="#Page_155">155</a>, <a href="#Page_156">156</a>, <a href="#Page_165">165</a>, <a href="#Page_225">225</a> +</li><li> +Martin, <a href="#Page_201">201</a>, <a href="#Page_218">218</a> +</li><li> +Mating, difficulties of, <a href="#Page_172">172</a> +</li><li> +—— fortuitous, <a href="#Page_174">174</a> +</li><li> +Maximum number supportable in a given locality, <a href="#Page_49">49</a> +</li><li> +Meadow-Pipit, <a href="#Page_188">188</a> +</li><li> +Meeting places for antics, <a href="#Page_54">54</a>, <a href="#Page_63">63</a> +</li><li> +Mental Image, <a href="#Page_77">77</a> +</li><li> +Merlin, <a href="#Page_227">227</a> +</li><li> +Migration, <a href="#Page_3">3</a>-4 +</li><li> +—— distance no criterion, <a href="#Page_279">279</a> +</li><li> +—— its relation to territory, <a href="#Page_259">259</a> +</li><li> +Migration, origin of, <a href="#Page_260">260</a>, <a href="#Page_277">277</a> +</li><li> +—— phenomenon of, <a href="#Page_277">277</a> +</li><li> +Migratory instinct, <a href="#Page_37">37</a> +</li><li> +—— species more highly specialised than resident species, <a href="#Page_56">56</a> +</li><li> +Missel-Thrush, <a href="#Page_21">21</a> +</li><li> +Mobility of the land and stability of the water, <a href="#Page_260">260</a> +</li><li> +Moor-hen, <a href="#Page_61">61</a>, <a href="#Page_85">85</a>, <a href="#Page_103">103</a>, <a href="#Page_218">218</a>, <a href="#Page_250">250</a>, <a href="#Page_251">251</a> +</li><li> +Morgan, Professor Lloyd, on instinctive behaviour, <a href="#Page_74">74</a> +</li><li> +—— on emotional behaviour, <a href="#Page_114">114</a> +</li><li> +</li><li> +<span class="smcap">Nest,</span> cleaning of, <a href="#Page_180">180</a> +</li><li> +—— construction of, <a href="#Page_3">3</a> +</li><li> +Nests, removal of, for experiments, <a href="#Page_181">181</a>, <a href="#Page_185">185</a>, <a href="#Page_190">190</a>, <a href="#Page_213">213</a>, <a href="#Page_214">214</a> +</li><li> +Neutral feeding grounds, <a href="#Page_62">62</a>, <a href="#Page_125">125</a> +</li><li> +—— ground, <a href="#Page_98">98</a> +</li><li> +Newton, E., on the arrival at breeding stations of males before female, <a href="#Page_24">24</a>, <a href="#Page_35">35</a> +</li><li> +Nightingale, <a href="#Page_39">39</a>, <a href="#Page_156">156</a> +</li><li> +Notes of alarm, <a href="#Page_119">119</a> +</li><li> +—— of anger, <a href="#Page_119">119</a> +</li><li> +—— of recognition, <a href="#Page_139">139</a> +</li><li> +—— of warning, <a href="#Page_119">119</a>, <a href="#Page_139">139</a>, <a href="#Page_141">141</a>, <a href="#Page_145">145</a>, <a href="#Page_151">151</a>, <a href="#Page_153">153</a> +</li><li> +</li><li> +<span class="smcap">Offspring,</span> rearing of, <a href="#Page_3">3</a>, <a href="#Page_4">4</a> +</li><li> +Organic change, sexual, <a href="#Page_92">92</a>, <a href="#Page_123">123</a> +</li><li> +—— changes, <a href="#Page_65">65</a> +</li><li> +—— condition of Reeve, <a href="#Page_173">173</a> +</li><li> +Owl, Wood, <a href="#Page_156">156</a> +</li><li> +</li><li> +<span class="smcap">Paired</span> for life, <a href="#Page_55">55</a>-56 +</li><li> +Parental instinctive response, failure of, <a href="#Page_185">185</a> +</li><li> +Partridge, <a href="#Page_87">87</a>, <a href="#Page_218">218</a> +</li><li> +Persecution, Carrion Crow and Magpie, <a href="#Page_226">226</a> +<span class='pagenum'><a name="Page_306" id="Page_306">306</a></span> +Persecution, Carrion Crow and Rook, <a href="#Page_227">227</a> +</li><li> +—— House Sparrow and Martin, <a href="#Page_218">218</a> +</li><li> +—— Lapwing and Snipe, <a href="#Page_220">220</a> +</li><li> +—— Raven and Buzzard, <a href="#Page_217">217</a> +</li><li> +—— —— and Peregrine, <a href="#Page_216">216</a> +</li><li> +—— Starling and Woodpecker, <a href="#Page_218">218</a>, <a href="#Page_237">237</a> +</li><li> +Persistency to remain in territory, <a href="#Page_68">68</a> +</li><li> +Pied-Wagtail, <a href="#Page_86">86</a>, <a href="#Page_155">155</a> +</li><li> +Pigeon, Wood, <a href="#Page_219">219</a> +</li><li> +Pipit, Meadow, <a href="#Page_188">188</a> +</li><li> +—— Tree, <a href="#Page_51">51</a>, <a href="#Page_188">188</a>, <a href="#Page_189">189</a>, <a href="#Page_222">222</a>, <a href="#Page_244">244</a>, <a href="#Page_278">278</a> +</li><li> +Polyandrous females, <a href="#Page_144">144</a> +</li><li> +Predatory species, <a href="#Page_268">268</a> +</li><li> +Promiscuous pairing of Ruffs, <a href="#Page_172">172</a> +</li><li> +Proximity to food-supply necessary for rearing young, <a href="#Page_179">179</a>, <a href="#Page_195">195</a> +</li><li> +<i>Psychology, Manual of</i>, <a href="#Page_1">1</a> +</li><li> +Puffin, <a href="#Page_63">63</a>, <a href="#Page_116">116</a>, <a href="#Page_200">200</a> +</li><li> +Pugnacious instinct, <a href="#Page_87">87</a>-109 +</li><li> +Pugnacity, <a href="#Page_11">11</a>, <a href="#Page_62">62</a> +</li><li> +—— of females to obtain mates, <a href="#Page_109">109</a>-118 +</li><li> +—— of males, prior to mating-season, <a href="#Page_77">77</a>-81 +</li><li> +—— of Moor-Hen, <a href="#Page_218">218</a> +</li><li> +</li><li> +<span class="smcap">Racial</span> preparation, <a href="#Page_41">41</a>, <a href="#Page_43">43</a>, <a href="#Page_46">46</a>, <a href="#Page_67">67</a>, <a href="#Page_205">205</a>, <a href="#Page_206">206</a>, <a href="#Page_266">266</a> +</li><li> +Rail, Water, <a href="#Page_218">218</a> +</li><li> +Raven, <a href="#Page_48">48</a>, <a href="#Page_202">202</a>, <a href="#Page_216">216</a> +</li><li> +Razor-bill, <a href="#Page_63">63</a>, <a href="#Page_64">64</a>, <a href="#Page_200">200</a>, <a href="#Page_247">247</a> +</li><li> +Readjustment of territory, <a href="#Page_146">146</a> +</li><li> +Rearing of offspring, <a href="#Page_3">3</a>, <a href="#Page_4">4</a> +</li><li> +Red-backed Shrike, <a href="#Page_39">39</a>, <a href="#Page_50">50</a>, <a href="#Page_51">51</a>, <a href="#Page_156">156</a> +</li><li> +Redbreast, <a href="#Page_47">47</a> +</li><li> +Redshank, <a href="#Page_139">139</a> +</li><li> +Redwing, <a href="#Page_124">124</a> +</li><li> +Redstart, <a href="#Page_230">230</a>, <a href="#Page_244">244</a> +</li><li> +Reed-Bunting, <a href="#Page_28">28</a>, <a href="#Page_68">68</a>, <a href="#Page_69">69</a>, <a href="#Page_85">85</a>, <a href="#Page_104">104</a>, <a href="#Page_132">132</a>, <a href="#Page_156">156</a>, <a href="#Page_158">158</a>, <a href="#Page_160">160</a>, <a href="#Page_244">244</a>, <a href="#Page_246">246</a>, <a href="#Page_273">273</a> +</li><li> +Reed-Warbler, <a href="#Page_49">49</a>, <a href="#Page_51">51</a>, <a href="#Page_68">68</a>, <a href="#Page_81">81</a>, <a href="#Page_132">132</a>, <a href="#Page_140">140</a>, <a href="#Page_152">152</a>, <a href="#Page_153">153</a>, <a href="#Page_211">211</a>, <a href="#Page_225">225</a> +</li><li> +Reeve, <a href="#Page_171">171</a> +</li><li> +Relation of song to the territory, <a href="#Page_119">119</a>-68 +</li><li> +—— of territory to migration, <a href="#Page_259">259</a> +</li><li> +—— of territory to the system of reproduction, <a href="#Page_169">169</a>-214 +</li><li> +Relationship to a territory, <a href="#Page_169">169</a> +</li><li> +Reproduction, <a href="#Page_14">14</a>, <a href="#Page_15">15</a> +</li><li> +—— and territory, <a href="#Page_169">169</a>-214 +</li><li> +—— attainment of, <a href="#Page_2">2</a>, <a href="#Page_6">6</a>, <a href="#Page_37">37</a> +</li><li> +—— goal of, <a href="#Page_6">6</a> +</li><li> +Ringed Guillemot, <a href="#Page_64">64</a> +</li><li> +Robbery of territory, <a href="#Page_104">104</a>-107 +</li><li> +Rock-formation, suitability for Guillemots nesting on, <a href="#Page_196">196</a> +</li><li> +Rook, <a href="#Page_202">202</a>, <a href="#Page_227">227</a> +</li><li> +Routine behaviour, <a href="#Page_262">262</a> +</li><li> +Ruff, <a href="#Page_54">54</a>, <a href="#Page_63">63</a>, <a href="#Page_172">172</a> +</li><li> +—— meeting places for conflicts, <a href="#Page_54">54</a> +</li><li> +Ruffs, promiscuous pairing of, <a href="#Page_172">172</a> +</li><li> +</li><li> +<span class="smcap">Savi's</span> Warbler, <a href="#Page_139">139</a> +</li><li> +Sedge-Warbler, <a href="#Page_25">25</a>, <a href="#Page_44">44</a>, <a href="#Page_152">152</a>, <a href="#Page_226">226</a>, <a href="#Page_244">244</a> +</li><li> +Selous, E., on the life-history of Ruffs and Reeves, <a href="#Page_172">172</a> +</li><li> +—— on meeting places for conflicts and antics, <a href="#Page_54">54</a> +</li><li> +—— on the meeting places of Black Grouse, <a href="#Page_63">63</a> +</li><li> +Service, Robert, on flocks of unmated Sedge-Warblers, <a href="#Page_44">44</a>, <a href="#Page_45">45</a> +</li><li> +Sexual behaviour, <a href="#Page_3">3</a> +</li><li> +—— conflicts, <a href="#Page_10">10</a> +</li><li> +—— development, <a href="#Page_6">6</a> +</li><li> +—— function, discharge of, <a href="#Page_2">2</a>, <a href="#Page_3">3</a>, <a href="#Page_26">26</a> +</li><li> +—— impulse of females, <a href="#Page_13">13</a> +<span class='pagenum'><a name="Page_307" id="Page_307">307</a></span> +Sexual instinct in the migratory male, <a href="#Page_26">26</a> +</li><li> +—— of Reeve, <a href="#Page_173">173</a> +</li><li> +—— —— reawakening of, <a href="#Page_4">4</a>, <a href="#Page_18">18</a> +</li><li> +—— life of birds, <a href="#Page_1">1</a> +</li><li> +—— maturity, males arrive at, before females, <a href="#Page_36">36</a> +</li><li> +—— organic change, <a href="#Page_92">92</a>, <a href="#Page_123">123</a> +</li><li> +—— selection, <a href="#Page_166">166</a> +</li><li> +Shag, <a href="#Page_121">121</a> +</li><li> +Shrike, Red-backed, <a href="#Page_39">39</a>, <a href="#Page_50">50</a>, <a href="#Page_51">51</a>, <a href="#Page_156">156</a> +</li><li> +Skylark, <a href="#Page_188">188</a>, <a href="#Page_236">236</a>, <a href="#Page_244">244</a> +</li><li> +Snipe, <a href="#Page_153">153</a>, <a href="#Page_156">156</a>, <a href="#Page_219">219</a>, <a href="#Page_220">220</a> +</li><li> +Sociability when not paired, <a href="#Page_125">125</a>, <a href="#Page_126">126</a> +</li><li> +Song, as an aid in searching for a mate, <a href="#Page_12">12</a> +</li><li> +—— its influence on mating, <a href="#Page_167">167</a> +</li><li> +—— origin of, <a href="#Page_138">138</a> +</li><li> +—— relation to reproduction, <a href="#Page_123">123</a> +</li><li> +—— relation to territory, <a href="#Page_119">119</a>-168 +</li><li> +—— volume of, influenced by age, seasonal sexual development, or isolation, <a href="#Page_166">166</a> +</li><li> +Song-Thrush, <a href="#Page_222">222</a>, <a href="#Page_244">244</a> +</li><li> +Sparrow, House, <a href="#Page_218">218</a> +</li><li> +Sparrow-Hawk, <a href="#Page_269">269</a> +</li><li> +Spring, at approach of, birds lose their shyness, <a href="#Page_138">138</a> +</li><li> +Stability of the water and mobility of the land, <a href="#Page_260">260</a> +</li><li> +Starling, <a href="#Page_217">217</a>, <a href="#Page_218">218</a>, <a href="#Page_237">237</a>, <a href="#Page_251">251</a> +</li><li> +Stimulation, internal, <a href="#Page_62">62</a>, <a href="#Page_123">123</a> +</li><li> +—— question of, <a href="#Page_284">284</a> +</li><li> +Stonechat, 87 <a href="#Page_187">187</a>, <a href="#Page_188">188</a>, <a href="#Page_189">189</a>, <a href="#Page_222">222</a>, <a href="#Page_233">233</a>, <a href="#Page_234">234</a> +</li><li> +Stout, Dr, <i>Manual of Psychology</i>, <a href="#Page_1">1</a>, <a href="#Page_77">77</a> +</li><li> +Struggle for existence, <a href="#Page_294">294</a> +</li><li> +Susceptibility to position, <a href="#Page_96">96</a> +</li><li> +Swallow, <a href="#Page_21">21</a>, <a href="#Page_156">156</a>, <a href="#Page_278">278</a> +</li><li> +</li><li> +<span class="smcap">Territory,</span> <a href="#Page_1">1</a>, <a href="#Page_5">5</a> +</li><li> +—— adjustment of, <a href="#Page_10">10</a> +</li><li> +Territory and reproduction, <a href="#Page_169">169</a>-214 +</li><li> +—— breeding, <a href="#Page_2">2</a>, <a href="#Page_3">3</a>, <a href="#Page_7">7</a> +</li><li> +—— dates of acquisition of, <a href="#Page_33">33</a> +</li><li> +—— defence of, <a href="#Page_6">6</a> +</li><li> +—— desertion of, after rearing young, <a href="#Page_276">276</a> +</li><li> +—— disposition to defend, <a href="#Page_73">73</a>-118 +</li><li> +—— disposition to secure, <a href="#Page_6">6</a>, <a href="#Page_20">20</a>-72 +</li><li> +—— establishment of, <a href="#Page_74">74</a>, <a href="#Page_285">285</a> +</li><li> +—— evolution of, <a href="#Page_176">176</a> +</li><li> +—— failure to secure, <a href="#Page_286">286</a> +</li><li> +—— fights for, <a href="#Page_10">10</a>, <a href="#Page_11">11</a>, <a href="#Page_13">13</a>, <a href="#Page_62">62</a> +</li><li> +—— ownership of, <a href="#Page_189">189</a> +</li><li> +—— possession of, a stimulus to song, <a href="#Page_136">136</a> +</li><li> +—— its relation to migration, <a href="#Page_259">259</a> +</li><li> +—— its relation to reproduction, <a href="#Page_169">169</a>-214 +</li><li> +—— readjustment of, <a href="#Page_147">147</a> +</li><li> +—— restriction of, advantageous for mating, <a href="#Page_172">172</a> +</li><li> +—— restricted, <a href="#Page_8">8</a>, <a href="#Page_9">9</a>, <a href="#Page_30">30</a>, <a href="#Page_50">50</a>, <a href="#Page_58">58</a>, <a href="#Page_64">64</a> +</li><li> +—— separate for male and female Cuckoo, <a href="#Page_144">144</a> +</li><li> +—— song, its relation to the, <a href="#Page_119">119</a>-68 +</li><li> +—— temporary desertion of, <a href="#Page_28">28</a>, <a href="#Page_35">35</a>, <a href="#Page_58">58</a>, <a href="#Page_59">59</a> +</li><li> +—— and hostility, relationship between, <a href="#Page_242">242</a> +</li><li> +Thrush, Song, <a href="#Page_222">222</a>, <a href="#Page_244">244</a> +</li><li> +Tit, Blue, <a href="#Page_221">221</a>, <a href="#Page_226">226</a> +</li><li> +—— Great, <a href="#Page_221">221</a> +</li><li> +—— Long-tailed, <a href="#Page_226">226</a> +</li><li> +Tradition, <a href="#Page_300">300</a> +</li><li> +Tree-Pipit, <a href="#Page_51">51</a>, <a href="#Page_188">188</a>, <a href="#Page_189">189</a>, <a href="#Page_222">222</a>, <a href="#Page_232">232</a>, <a href="#Page_244">244</a>, <a href="#Page_278">278</a> +</li><li> +Turtle-Dove, <a href="#Page_126">126</a>, <a href="#Page_232">232</a> +</li><li> +</li><li> +<span class="smcap">Union</span> of sexes, <a href="#Page_12">12</a> +</li><li> +Ussher, H. B., on the hostility between Choughs and Hooded Crows and Choughs and Ravens, <a href="#Page_227">227</a> +</li><li> +<span class='pagenum'><a name="Page_308" id="Page_308">308</a></span> +</li><li> +<span class="smcap">Vocal</span> Imitation, <a href="#Page_156">156</a>, <a href="#Page_157">157</a>, <a href="#Page_161">161</a> +</li><li> +Voice calls of Curlew, <a href="#Page_263">263</a> +</li><li> +</li><li> +<span class="smcap">Wagtail,</span> Pied, <a href="#Page_86">86</a>, <a href="#Page_155">155</a> +</li><li> +—— Yellow, <a href="#Page_278">278</a> +</li><li> +Wanderings from land, Guillemots, <a href="#Page_193">193</a> +</li><li> +Warbler, Garden, <a href="#Page_223">223</a>, <a href="#Page_225">225</a>, <a href="#Page_230">230</a> +</li><li> +—— Grasshopper, <a href="#Page_39">39</a>, <a href="#Page_131">131</a>, <a href="#Page_139">139</a>, <a href="#Page_155">155</a>, <a href="#Page_187">187</a>, <a href="#Page_244">244</a> +</li><li> +—— Marsh, <a href="#Page_39">39</a>, <a href="#Page_40">40</a>, <a href="#Page_52">52</a>, <a href="#Page_81">81</a>, <a href="#Page_132">132</a>, <a href="#Page_140">140</a>, <a href="#Page_155">155</a>, <a href="#Page_156">156</a>, <a href="#Page_225">225</a> +</li><li> +—— Reed, <a href="#Page_49">49</a>, <a href="#Page_51">51</a>, <a href="#Page_68">68</a>, <a href="#Page_81">81</a>, <a href="#Page_132">132</a>, <a href="#Page_140">140</a>, <a href="#Page_152">152</a>, <a href="#Page_153">153</a>, <a href="#Page_211">211</a>, <a href="#Page_225">225</a> +</li><li> +—— Savi's, <a href="#Page_139">139</a> +</li><li> +—— Sedge, <a href="#Page_25">25</a>, <a href="#Page_44">44</a>, <a href="#Page_152">152</a>, <a href="#Page_226">226</a>, <a href="#Page_244">244</a> +</li><li> +—— Willow, <a href="#Page_25">25</a>, <a href="#Page_47">47</a>, <a href="#Page_50">50</a>, <a href="#Page_51">51</a>, <a href="#Page_80">80</a>, <a href="#Page_91">91</a>, <a href="#Page_140">140</a>, <a href="#Page_187">187</a>, <a href="#Page_211">211</a>, <a href="#Page_232">232</a>, <a href="#Page_244">244</a>, <a href="#Page_273">273</a> +</li><li> +—— Wood, <a href="#Page_50">50</a>, <a href="#Page_51">51</a>, <a href="#Page_132">132</a>, <a href="#Page_221">221</a> +</li><li> +Warfare between different species and its relation to the territory, <a href="#Page_215">215</a>-58 +</li><li> +Warning notes, <a href="#Page_119">119</a> +</li><li> +—— of danger, <a href="#Page_269">269</a> +</li><li> +Water Rail, <a href="#Page_218">218</a> +</li><li> +Wheatear, <a href="#Page_25">25</a>, <a href="#Page_51">51</a> +</li><li> +Whimbrel, <a href="#Page_140">140</a> +</li><li> +Whinchat, <a href="#Page_39">39</a>, <a href="#Page_50">50</a>, <a href="#Page_51">51</a>, <a href="#Page_81">81</a>, <a href="#Page_222">222</a>, <a href="#Page_232">232</a>, <a href="#Page_233">233</a>, <a href="#Page_234">234</a>, <a href="#Page_244">244</a> +</li><li> +Whitethroat, <a href="#Page_25">25</a>, <a href="#Page_50">50</a>, <a href="#Page_68">68</a>, <a href="#Page_69">69</a>, <a href="#Page_124">124</a>, <a href="#Page_140">140</a>, <a href="#Page_182">182</a>, <a href="#Page_187">187</a>, <a href="#Page_189">189</a>, <a href="#Page_190">190</a>, <a href="#Page_213">213</a>, <a href="#Page_230">230</a>, <a href="#Page_244">244</a> +</li><li> +—— Lesser, <a href="#Page_230">230</a>, <a href="#Page_244">244</a> +</li><li> +Wild Duck, <a href="#Page_250">250</a> +</li><li> +Will, the, to fight, <a href="#Page_102">102</a> +</li><li> +Willow-Warbler, <a href="#Page_25">25</a>, <a href="#Page_47">47</a>, <a href="#Page_50">50</a>, <a href="#Page_51">51</a>, <a href="#Page_80">80</a>, <a href="#Page_91">91</a>, <a href="#Page_140">140</a>, <a href="#Page_187">187</a>, <a href="#Page_211">211</a>, <a href="#Page_232">232</a>, <a href="#Page_244">244</a>, <a href="#Page_273">273</a> +</li><li> +Winter assemblies, <a href="#Page_262">262</a>-63 +</li><li> +Witherby, H. F., in <i>British Birds</i>, on the return to former breeding-ground, <a href="#Page_281">281</a> +</li><li> +Wood-Owl, <a href="#Page_156">156</a> +</li><li> +Wood-Pigeon, <a href="#Page_219">219</a> +</li><li> +Wood-Warbler, <a href="#Page_50">50</a>, <a href="#Page_51">51</a>, <a href="#Page_132">132</a>, <a href="#Page_221">221</a> +</li><li> +Woodpecker, Lesser Spotted, <a href="#Page_237">237</a> +</li><li> +—— Great Spotted, <a href="#Page_237">237</a>, <a href="#Page_238">238</a> +</li><li> +—— Green, <a href="#Page_20">20</a>, <a href="#Page_71">71</a>, <a href="#Page_156">156</a>, <a href="#Page_208">208</a>, <a href="#Page_218">218</a>, <a href="#Page_237">237</a> +</li><li> +Wren, <a href="#Page_244">244</a> +</li><li> +</li><li> +<span class="smcap">Yellow</span> Bunting, <a href="#Page_28">28</a>, <a href="#Page_30">30</a>, <a href="#Page_47">47</a>, <a href="#Page_64">64</a>, <a href="#Page_140">140</a>, <a href="#Page_159">159</a>, <a href="#Page_162">162</a>, <a href="#Page_183">183</a>, <a href="#Page_187">187</a>, <a href="#Page_188">188</a>, <a href="#Page_189">189</a>, <a href="#Page_235">235</a>, <a href="#Page_236">236</a>, <a href="#Page_286">286</a> +</li><li> +Young die in nest from exposure, <a href="#Page_184">184</a>, <a href="#Page_185">185</a> +</li></ul> + + +<hr /> +<h3>PRINTED BY OLIVER AND BOYD, EDINBURGH, SCOTLAND</h3> + + + + + + + +<pre> + + + + + +End of Project Gutenberg's Territory in Bird Life, by H. 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