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diff --git a/32855-h/32855-h.htm b/32855-h/32855-h.htm new file mode 100644 index 0000000..f6e1f7c --- /dev/null +++ b/32855-h/32855-h.htm @@ -0,0 +1,4149 @@ +<!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 http-equiv="Content-Type" content="text/html;charset=iso-8859-1" /> + <title> + The Project Gutenberg eBook of Natural History of the Bell Vireo, Vireo bellii Audubon, by Jon C. Barlow. + </title> + <style type="text/css"> + + p { margin-top: .75em; + text-align: justify; + margin-bottom: .75em; + } + h1,h2,h3,h4,h5,h6 { + text-align: center; /* all headings centered */ + clear: both; + } + hr { width: 33%; + margin-top: 2em; + margin-bottom: 2em; + margin-left: auto; + margin-right: auto; + clear: both; + } + + table {margin-left: auto; margin-right: auto;} + + body{margin-left: 10%; + margin-right: 10%; + } + + .pagenum { /* uncomment the next line for invisible page numbers */ + /* visibility: hidden; */ + position: absolute; + left: 92%; + font-size: smaller; + text-align: right; + } /* page numbers */ + + .blockquot{margin-left: 10%; margin-right: 10%; text-indent: -4em;} + + .center {text-align: center;} + .smcap {font-variant: small-caps;} + + .caption {font-weight: bold;} + + .figcenter {margin: auto; text-align: center;} + + .footnotes {border: dashed 1px;} + .footnote {margin-left: 10%; margin-right: 10%; font-size: 0.9em;} + .footnote .label {position: absolute; right: 84%; text-align: right;} + .fnanchor {vertical-align: super; font-size: .8em; text-decoration: none;} + + </style> + </head> +<body> + + +<pre> + +The Project Gutenberg EBook of Natural History of the Bell Vireo, Vireo +bellii Audubon, by Jon C. Barlow + +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: Natural History of the Bell Vireo, Vireo bellii Audubon + +Author: Jon C. Barlow + +Release Date: June 17, 2010 [EBook #32855] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK THE BELL VIREO *** + + + + +Produced by Chris Curnow, Joseph Cooper and the Online +Distributed Proofreading Team at http://www.pgdp.net + + + + + + +</pre> + + + + +<h4><big><span class="smcap">University of Kansas Publications</span></big><br /> +<span class="smcap">Museum of Natural History</span><br /> +<br /> +Volume 12, No. 5, pp. 241-296, 6 figs.<br /> +March 7, 1962</h4> + +<h1>Natural History of the Bell Vireo,<br /> +Vireo bellii Audubon</h1> + +<h3>BY</h3> + +<h3>JON C. BARLOW</h3> + +<h3><span class="smcap">University of Kansas</span><br /> +<span class="smcap">Lawrence</span><br /> +1962</h3> + + + +<hr style="width: 65%;" /> +<h4><span class="smcap">University of Kansas Publications, Museum of Natural History</span><br /> +Editors: E. Raymond Hall, Chairman, Theodore H. Eaton, Jr., Henry S. Fitch<br /> +<br /> +Volume 12, No. 5, pp. 241-296, 6 figs.<br /> +Published March 7, 1962<br /> +<br /> +<big><span class="smcap">University of Kansas</span><br /> +Lawrence, Kansas</big></h4> + +<h5><small>PRINTED BY<br /> +JEAN M. NEIBARGER, STATE PRINTER<br /> +TOPEKA, KANSAS<br /> +1962</small><br /> +<br /> +29-1506</h5> + + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_243" id="Page_243">[Pg 243]</a></span></p> +<h1>Natural History of the Bell Vireo,<br /> +Vireo bellii Audubon</h1> + +<h4>BY</h4> + +<h4>JON C. BARLOW</h4> + + +<hr style="width: 15%;" /> +<h2><a name="CONTENTS" id="CONTENTS"></a>CONTENTS</h2> + +<table border="0" cellpadding="5" cellspacing="0" summary="Table of Contents"> +<tr> + <td> </td> + <td align="right"><small>PAGE</small></td> +</tr> +<tr> + <td><a href="#CONTENTS"><span class="smcap">Contents</span></a></td> + <td align="right"><a href="#Page_243">243</a></td> +</tr> +<tr> + <td><a href="#INTRODUCTION"><span class="smcap">Introduction</span></a></td> + <td align="right"><a href="#Page_245">245</a></td> +</tr> +<tr> + <td><a href="#ACKNOWLEDGMENTS"><span class="smcap">Acknowledgments</span></a></td> + <td align="right"><a href="#Page_245">245</a></td> +</tr> +<tr> + <td><a href="#METHODS_OF_STUDY"><span class="smcap">Methods of Study</span></a></td> + <td align="right"><a href="#Page_246">246</a></td> +</tr> +<tr> + <td><a href="#STUDY_AREA"><span class="smcap">Study Area</span></a></td> + <td align="right"><a href="#Page_247">247</a></td> +</tr> +<tr> + <td> Considerations of Habitat</td> + <td align="right"><a href="#Page_248">248</a></td> +</tr> +<tr> + <td><a href="#SEASONAL_MOVEMENT"><span class="smcap">Seasonal Movement</span></a></td> + <td align="right"><a href="#Page_250">250</a></td> +</tr> +<tr> + <td> Arrival in Spring</td> + <td align="right"><a href="#Page_250">250</a></td> +</tr> +<tr> + <td> Fall Departure</td> + <td align="right"><a href="#Page_251">251</a></td> +</tr> +<tr> + <td><a href="#GENERAL_BEHAVIOR"><span class="smcap">General Behavior</span></a></td> + <td align="right"><a href="#Page_252">252</a></td> +</tr> +<tr> + <td> Flight</td> + <td align="right"><a href="#Page_252">252</a></td> +</tr> +<tr> + <td> Foraging and Food Habits</td> + <td align="right"><a href="#Page_252">252</a></td> +</tr> +<tr> + <td> Bathing</td> + <td align="right"><a href="#Page_253">253</a></td> +</tr> +<tr> + <td><a href="#VOCALIZATIONS"><span class="smcap">Vocalizations</span></a></td> + <td align="right"><a href="#Page_254">254</a></td> +</tr> +<tr> + <td> Singing Postures</td> + <td align="right"><a href="#Page_255">255</a></td> +</tr> +<tr> + <td> Flight Song</td> + <td align="right"><a href="#Page_255">255</a></td> +</tr> +<tr> + <td> Daily Frequency of Song</td> + <td align="right"><a href="#Page_255">255</a></td> +</tr> +<tr> + <td> Types of Vocalizations</td> + <td align="right"><a href="#Page_255">255</a></td> +</tr> +<tr> + <td><a href="#TERRITORIALITY"><span class="smcap">Territoriality</span></a></td> + <td align="right"><a href="#Page_258">258</a></td> +</tr> +<tr> + <td> Establishment of Territory</td> + <td align="right"><a href="#Page_259">259</a></td> +</tr> +<tr> + <td> Size of Territories</td> + <td align="right"><a href="#Page_259">259</a></td> +</tr> +<tr> + <td> Permanence of Territories</td> + <td align="right"><a href="#Page_260">260</a></td> +</tr> +<tr> + <td> Maintenance of Territory</td> + <td align="right"><a href="#Page_260">260</a></td> +</tr> +<tr> + <td> Aggressive Behavior of the Female</td> + <td align="right"><a href="#Page_264">264</a></td> +</tr> +<tr> + <td> Interspecific Relationships</td> + <td align="right"><a href="#Page_264">264</a></td> +</tr> +<tr> + <td> Discussion</td> + <td align="right"><a href="#Page_265">265</a></td> +</tr> +<tr> + <td><a href="#COURTSHIP_BEHAVIOR"><span class="smcap">Courtship Behavior</span></a></td> + <td align="right"><a href="#Page_267">267</a></td> +</tr> +<tr> + <td> Displays and Postures</td> + <td align="right"><a href="#Page_268">268</a></td> +</tr> +<tr> + <td> Discussion<span class='pagenum'><a name="Page_244" id="Page_244">[Pg 244]</a></span></td> + <td align="right"><a href="#Page_270">270</a></td> +</tr> +<tr> + <td><a href="#SELECTION_OF_NEST-SITE_AND_NESTBUILDING"><span class="smcap">Selection of Nest-site and Nestbuilding</span></a></td> + <td align="right"><a href="#Page_272">272</a></td> +</tr> +<tr> + <td> Building</td> + <td align="right"><a href="#Page_274">274</a></td> +</tr> +<tr> + <td> Gathering of Nesting Materials</td> + <td align="right"><a href="#Page_276">276</a></td> +</tr> +<tr> + <td> Length and Hours of Nestbuilding</td> + <td align="right"><a href="#Page_277">277</a></td> +</tr> +<tr> + <td> Abortive Nestbuilding Efforts</td> + <td align="right"><a href="#Page_277">277</a></td> +</tr> +<tr> + <td> Renesting</td> + <td align="right"><a href="#Page_277">277</a></td> +</tr> +<tr> + <td> The Nest</td> + <td align="right"><a href="#Page_277">277</a></td> +</tr> +<tr> + <td><a href="#EGGLAYING_AND_INCUBATION"><span class="smcap">Egglaying and Incubation</span></a></td> + <td align="right"><a href="#Page_278">278</a></td> +</tr> +<tr> + <td> Egglaying</td> + <td align="right"><a href="#Page_278">278</a></td> +</tr> +<tr> + <td> Clutch-size</td> + <td align="right"><a href="#Page_279">279</a></td> +</tr> +<tr> + <td> Incubation</td> + <td align="right"><a href="#Page_280">280</a></td> +</tr> +<tr> + <td> The Roles of the Sexes in Incubation</td> + <td align="right"><a href="#Page_280">280</a></td> +</tr> +<tr> + <td> Relief of Partners in Incubation</td> + <td align="right"><a href="#Page_283">283</a></td> +</tr> +<tr> + <td><a href="#NESTLING_PERIOD"><span class="smcap">Nestling Period</span></a></td> + <td align="right"><a href="#Page_283">283</a></td> +</tr> +<tr> + <td> Hatching Sequence</td> + <td align="right"><a href="#Page_283">283</a></td> +</tr> +<tr> + <td> Development of the Nestlings</td> + <td align="right"><a href="#Page_284">284</a></td> +</tr> +<tr> + <td> Parental Behavior</td> + <td align="right"><a href="#Page_285">285</a></td> +</tr> +<tr> + <td> Feeding of the Nestlings</td> + <td align="right"><a href="#Page_286">286</a></td> +</tr> +<tr> + <td> Nest Sanitation</td> + <td align="right"><a href="#Page_287">287</a></td> +</tr> +<tr> + <td> Fledging</td> + <td align="right"><a href="#Page_287">287</a></td> +</tr> +<tr> + <td> Nest Parasites</td> + <td align="right"><a href="#Page_287">287</a></td> +</tr> +<tr> + <td><a href="#FLEDGLING_LIFE"><span class="smcap">Fledgling Life</span></a></td> + <td align="right"><a href="#Page_288">288</a></td> +</tr> +<tr> + <td> Second Broods</td> + <td align="right"><a href="#Page_288">288</a></td> +</tr> +<tr> + <td><a href="#REPRODUCTIVE_SUCCESS"><span class="smcap">Reproductive Success</span></a></td> + <td align="right"><a href="#Page_289">289</a></td> +</tr> +<tr> + <td> Behavior</td> + <td align="right"><a href="#Page_290">290</a></td> +</tr> +<tr> + <td> Predation</td> + <td align="right"><a href="#Page_291">291</a></td> +</tr> +<tr> + <td> Cowbird Parasitism</td> + <td align="right"><a href="#Page_291">291</a></td> +</tr> +<tr> + <td><a href="#SUMMARY"><span class="smcap">Summary</span></a></td> + <td align="right"><a href="#Page_292">292</a></td> +</tr> +<tr> + <td><a href="#LITERATURE_CITED"><span class="smcap">Literature Cited</span></a></td> + <td align="right"><a href="#Page_294">294</a></td> +</tr> +</table> + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_245" id="Page_245">[Pg 245]</a></span></p> +<h2><a name="INTRODUCTION" id="INTRODUCTION"></a>INTRODUCTION</h2> + + +<p>The Bell Vireo (<i>Vireo bellii</i> Aud.) is a summer resident in riparian +and second growth situations in the central United States south of +North Dakota. In the last two decades this bird has become fairly +common in western, and to a lesser extent in central, Indiana and +is apparently shifting its breeding range eastward in that state +(Mumford, 1952; Nolan, 1960). In northeastern Kansas the species +breeds commonly and occurs in most tracts of suitable habitat.</p> + +<p>The literature contains several reports dealing exclusively with +the Bell Vireo, notably those of Bennett (1917), Nice (1929), Du +Bois (1940), Pitelka and Koestner (1942), Hensley (1950) and +Mumford (1952). Bent (1950) has summarized the information +available on the species through 1943. Nolan (1960) recently completed +an extensive report based on a small, banded population at +Bloomington, Monroe County, Indiana. He validated for this +species many points of natural history previously based on estimates +and approximations, especially concerning the post-fledging life of +the young and the movement of the adults from one "home range" +to another in the course of a single season.</p> + +<p>None of these reports, however, has emphasized the ritualized +behavioral patterns associated with the maintenance of territory +and with courtship. Among the North American Vireonidae, the +behavior of the Red-eyed Vireo (<i>Vireo olivaceus</i>) is best documented +(Sutton, 1949; Lawrence, 1953; Southern, 1958). With this +species authors have concentrated on the mechanics of the breeding +season and their reports contain little discussion of the aggressive +and epigamic behavior of the bird.</p> + +<p>The amount of information on the ritualized behavior of the Bell +Vireo and related species heretofore has been meager. I observed +breeding behavior from its inception in early May through the +summer of 1960. It is hoped the resulting information will serve +as a basis of comparison in future studies of behavior of vireos; such +ethological data are becoming increasingly important, especially as +an aid in systematics.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="ACKNOWLEDGMENTS" id="ACKNOWLEDGMENTS"></a>ACKNOWLEDGMENTS</h2> + + +<p>To professors Frank B. Cross, Henry S. Fitch, and Richard F. +Johnston of the Department of Zoology of the University of Kansas +I am grateful for comments and suggestions in various phases of +the study and the preparation of the manuscript. Professor Johnston +<span class='pagenum'><a name="Page_246" id="Page_246">[Pg 246]</a></span> +also made available data on the breeding of the Bell Vireo from the +files of the Kansas Ornithological Society. I am indebted to my +wife, Judith Barlow, for many hours of typing and copy reading. +Mrs. Lorna Cordonnier prepared the map, Thomas H. Swearingen +drew the histograms, and Professor A. B. Leonard photographed +and developed the histograms. Dr. Robert M. Mengel contributed +the sketch of the Bell Vireo and George P. Young prepared the +dummy Bell Vireo used in the field work. Thomas R. Barlow, +Donald A. Distler, Abbot S. Gaunt, John L. Lenz, Gary L. Packard, +A. Wayne Wiens, and John Wellman assisted in various phases of +the field work.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="METHODS_OF_STUDY" id="METHODS_OF_STUDY"></a>METHODS OF STUDY</h2> + + +<p>Daily observations were made from May 11 to June 26 in 1959 +and from April 15 through July 15 in 1960. Six additional visits +were made to the study area in September of 1959, and ten others +in July and August, 1960. Periods of from one hour to eleven hours +were spent in the field each day, and a total of about five hundred +hours were logged in the field.</p> + +<p>Each territory was visited for at least five minutes each day but +more often for twenty minutes. The breeding activities of the pairs +were rarely synchronous. Consequently several stages in the cycle +of building were simultaneously available for study.</p> + +<p>Nine young and one adult were banded in 1959. No Bell Vireos +were banded in 1960. Individual pairs could be recognized because +of their exclusive use of certain segments of the study area +and by the individual variation in the song of the males. Sexes +were distinguishable on the basis of differences in vocalizations and +plumages.</p> + +<p>Most nests were located by the observer searching, watching a +pair engaged in building, or following a singing male until the +increased tempo of his song indicated proximity to a nest. As the +season progressed and the foliage grew more dense, it became +increasingly difficult to locate completed nests. Blinds were unnecessary +because of the density of vegetation. Observations were +facilitated by a 7 × 50 binocular. Data were recorded on the spot +in a field notebook. Eggs were numbered by means of Higgins +Engrossing ink as they were laid.</p> + +<p>Individual trees in which males sang most were marked over a +three-week period. Then the distances between the most remote +perches were paced. These distances aided in determining the +<span class='pagenum'><a name="Page_247" id="Page_247">[Pg 247]</a></span> +size of the territories. The general configuration of the vegetation +within each territory determined the location of one or more boundaries +of the territory. Each territory was given a number, 1, 2, 3, +etc., as it was discovered; consequently there is no numerical relationship +between the designations of the territories established in +1959 and 1960. Nests within a territory were designated as 1-a, 1-b, +1-c, etc.</p> + +<p>Although experimentation was not a primary source of data, it +proved useful in certain instances. A stuffed Blue Jay elicited +mobbing behavior from nesting pairs. A dummy Bell Vireo elicited +both agonistic and epigamic behavior from nesting pairs, depending +on the phase of the nesting cycle.</p> + +<p>The temperature at the beginning of each day's work was taken +by means of a Weston dial thermometer. A hand counter and a +pocket watch having a second hand were used in determining such +data as frequency of song and periods of attentiveness by the sexes. +Histological cross-sections, prepared by A. Wayne Wiens, of the +ventral epidermis of both sexes were used to study brood patches.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="STUDY_AREA" id="STUDY_AREA"></a>STUDY AREA</h2> + + +<p>The intensive field work was on a 39-acre tract (fig. 1) extending +approximately 7/10 of a mile west from U. S. highway 59, which in +1959-1960 constituted the western city limit of Lawrence, Douglas +County, Kansas. The eastern boundary of the study area is +approximately 1-1/2 miles southwest of the County Courthouse in +Lawrence. The eastern ten acres is associated with the Laboratory of +Aquatic Biology of the University of Kansas. The 15 acres adjacent to +this on the southwest is owned by the University of Kansas Endowment +Association, but is used by Mr. E. H. Chamney for the grazing of +cattle. This portion is bounded on the west by a stone fence, beyond +which lies a 14-acre field of natural prairie owned by Dr. C. D. Clark +that is bordered on the extreme west by a narrow thicket of elm +saplings.</p> + +<p>The principal topographic feature of the area is an arm of Mount +Oread, that rises some 80 feet above the surrounding countryside. +About 200 feet from the crest of the southwestern slope of the hill a +40-foot-wide diversion terrace directs run-off toward the two-acre +reservoir that is the source of water for eight experimental fish +ponds of the laboratory.</p> + +<p>The predominant shrub-vegetation consists of Osage orange (<i>Maclura +pomifera</i>), honey locust (<i>Gleditsia triacanthos</i>), and +<span class='pagenum'><a name="Page_248" id="Page_248">[Pg 248]</a></span> +American elm (<i>Ulmus americana</i>). These saplings, ranging in height from +3 to 25 feet, grow in dense thickets as well as singly and in clumps of twos +and threes. Larger trees of these same species grow along the crest of +the hill, along the eastern and southeastern boundaries of the area, +and along the stone fence separating University land from that owned +by Dr. Clark. A dense growth of coralberry (<i>Symphoricarpos +orbiculatus</i>) forms the understory just below the crest of the hill. +Isolated clumps of dogwood (<i>Cornus drummondi</i>) and hawthorn +(<i>Crataegus mollis</i>) are scattered throughout the area. These species +of shrubs grow densely along the stone fence. The isolated thicket on +the Clark land is composed primarily of elm and boxelder (<i>Acer +negundo</i>), but includes scattered clumps of dogwood, Osage orange, and +honey locust. Poplars (<i>Populus deltoides</i>) are the only large trees +in this area.</p> + +<div class="figcenter" style="width: 90%;"> +<img src="images/i010.jpg" width="100%" alt="Fig. 1." title="Fig. 1." /> +<span class="caption"><span class="smcap">Fig. 1.</span> Map of the study +area near the University of Kansas Laboratory of Aquatic Biology. The +dashed lines mark the approximate territorial boundaries of the original +nine pairs of Bell Vireos from May 1960 to early June 1960.</span> +</div> + +<p>The open areas between the thickets are grown up in red top (<i>Triodia +flava</i>), bluestem (<i>Andropogon scoparius</i>), Switchgrass (<i>Panicum +virgatum</i>), Kentucky bluegrass (<i>Poa pratensis</i>), bush clover +(<i>Lespedeza capitata</i>) and mullen (<i>Verbascum thapsus</i>). Shrubby +vegetation occupies about 65 per cent of the total area, but in the +Clark portion constitutes only about 35 per cent of the ground cover.</p> + + +<h4><i>Considerations of Habitat</i></h4> + +<p>Nolan (1960:226), summarizing the available information on habitat +preferences of the Bell Vireo, indicates that this species tolerates +"a rather wide range of differences in cover." He pointed +<span class='pagenum'><a name="Page_249" id="Page_249">[Pg 249]</a></span> +out that a significant factor in habitat selection by this species may be +avoidance of the White-eyed Vireo (<i>V. griseus</i>) where the two species +are sympatric.</p> + +<p>In Douglas County where the Bell Vireo is the common species, the +White-eyed Vireo reaches the western extent of its known breeding +range in Kansas. At the Natural History Reservation of the University +of Kansas, where both species breed, the Bell Vireo occurs in "brush +thickets in open places" (Fitch, 1958:270) and the White-eyed Vireo +occupies "brush thickets, scrubby woodland and woodland edge" (Fitch, +<i>op. cit.</i>, 268). Along the Missouri River in extreme northeastern +Kansas, Linsdale (1928:588-589) found the White-eyed Vireo "at the +edge of the timber on the bluff, and in small clearings in the +timber," while "the Bell Vireo was characteristic of the growths of +willow thickets on newly formed sand bars." Elsewhere in northeastern +Kansas I have found the Bell Vireo in shrubbery of varying density and +often in habitat indistinguishable from that occupied by White-eyed +Vireos at the Natural History Reservation. In the periphery of the +region of sympatry the rarer species is confronted with a much higher +population density of the common species and consequently might well +be limited primarily to habitat less suitable for the common species. +This would seem to be the case in eastern Kansas, presuming that +interspecific competition exists.</p> + +<p>The Bell Vireo has followed the prairie peninsula into Indiana, aided +by the development of land for agriculture. In nearby Kentucky where +thousands of miles of forest edge are found, and where little brushy +habitat of the type preferred by the Bell Vireo occurs, the White-eyed +Vireo is abundant whereas the Bell Vireo is unknown as a breeding bird +(R. M. Mengel, personal communication).</p> + +<p>In more central portions of the area of sympatry, nevertheless, the +two species do occur within the same habitat (Ridgway, 1889:191; Bent, +1950:254) and occasionally within the same thicket (Ridgway, in +Pitelka and Koestner, 1942:105); their morphological and behavioral +differences, although slight, probably minimize interspecific +conflict. The Bell Vireo and the Black-capped Vireo (<i>V. +atricapillus</i>) have been found nesting in the same tree in Oklahoma by +Bunker (1910:72); the nest of the black-cap was situated centrally and +that of the Bell Vireo peripherally in the tree. Bell Vireos +invariably place their nests in the outer portions of trees and +peripherally in thickets. This placement would further obviate +interspecific conflict with the white-eye since its nests are placed +centrally in the denser portions of a thicket.</p> + +<p><span class='pagenum'><a name="Page_250" id="Page_250">[Pg 250]</a></span> +A critical feature of the habitat preferred by the Bell Vireo is the +presence of water. In far western Kansas this species is restricted to +riparian growth along the more permanent waterways. This in itself is +not adequate proof of the significance of water supply because thicket +growth in that part of the state is found only along waterways. The 20 +areas over the state that I have visited where Bell Vireos were +present were closely associated with at least a semi-permanent source +of water. Fifteen other areas indistinguishable from the 20 just +mentioned, but lacking a permanent supply of water, also lacked Bell +Vireos. Nevertheless areas in which Bell Vireos typically nest are +decidedly less mesic than those frequented by White-eyed Vireos.</p> + +<p>Once the Bell Vireo was probably more local in its distribution being +restricted to thickets associated with permanent water. Clearing of +woodland for agricultural and other use, and subsequent encroachment +of second growth concomitant with the creation of man-made lakes and +ponds, has greatly increased the available habitat for this bird. The +preferred species of shrubs for nesting are reported (Bent, 1950:254) +to be various wild plums (<i>Prunus sp.</i>). The widespread distribution +and abundance of the exotic Osage orange has greatly augmented the +supply of trees suitable for nesting.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="SEASONAL_MOVEMENT" id="SEASONAL_MOVEMENT"></a>SEASONAL MOVEMENT</h2> + + +<h4><i>Arrival in Spring</i></h4> + +<p>The subspecies of the Bell Vireo breeding in Kansas, <i>V. b. bellii</i>, +winters regularly from Guerrero and the Isthmus of Tehuantepec +south to Guatemala, El Salvador, and northern Nicaragua (A. O. U. +Check-list, Fifth Edition, 1957:469-470). In the United States +migrating birds are first recorded in early March (Cooke, 1909:119). +The Bell Vireo is a relatively slow migrator, moving primarily at +night and covering little more than 20 miles at a time (Cooke, +<i>op. cit.</i> 119). The average date of arrival, based on 27 records, for +northeastern Kansas is May 8; the earliest record is April 22, 1925, +from Manhattan, Riley County, Kansas (fig. 2-A).</p> + +<p>In 1959 the first bird arrived at the study tract about May 5. No +additional birds were heard singing until the third week of the +month, in which eight new males were noted. As mentioned, in +1960 field work was begun in mid-April and the study area was +traversed daily. No birds were detected until late afternoon of +May 3, when one, presumably a male, was seen foraging.</p> + +<p><span class='pagenum'><a name="Page_251" id="Page_251">[Pg 251]</a></span> +Lawrence (1953:50) has reported that males of the Red-eyed +Vireo precede females in the breeding area by as much as two +weeks; the male Red-eyed Vireo forages but sings little in the pre-nesting +period. The male Bell Vireo arrives first at the breeding +area but precedes the female by only a few days. On the morning +of May 4 the first male was singing from a number of perches while +ranging over an area of seven acres. This area encompassed territories +later occupied by three pairs, 2 (1960), 4 (1960), and 5 +(1960). Late on the afternoon of May 4 the first courtship songs +were heard and the first male was seen with a mate at 6:20 p.m. +Eight additional males arrived from May 6 through May 18. A +tenth male was discovered in the vicinity of territory 9 (1960) on +June 18, 1960.</p> + +<div class="figcenter" style="width: 80%;"> +<img src="images/i013.jpg" width="100%" alt="Fig. 2." title="Fig. 2." /> +<span class="caption"><span class="smcap">Fig. 2.</span> Seasonal movement as +indicated by the curve for spring arrival (A), based on the earliest dates for +27 years, and the curve for autumn departure (B), based on the latest dates for +21 years in northeastern Kansas.</span> +</div> + + +<h4><i>Fall Departure</i></h4> + +<p>The average date of departure for 21 years in northeastern Kansas is +September 3 (fig. 2-B). The earliest date is August 14 from Concordia, +Cloud County, Kansas (Porter, unpublished field notes). The latest +date is September 27 (Bent, 1950:262) from Onaga, Pottawatomie County, +Kansas. In 1959 the last vireo was seen at the study tract on +September 14. The birds do not all depart at the +<span class='pagenum'><a name="Page_252" id="Page_252">[Pg 252]</a></span> +same time. On September 1 there were still five singing males in the +study area; by September 10 there were three and on September 13, only +one.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="GENERAL_BEHAVIOR" id="GENERAL_BEHAVIOR"></a>GENERAL BEHAVIOR</h2> + + +<h4><i>Flight</i></h4> + +<p>In "straight-away" flight the Bell Vireo undulates slightly. In a +typical flight several rapid, but shallow, wing beats precede a fixed-wing +glide of from 1 to 15 feet in length. Because the wings are +extended horizontally during the glide, the bird does not move distinctly +above or below the plane of flight. The White-eyed Vireo +generally appears to be slower and more lethargic in flight than the +Bell Vireo. In the breeding season most flights of the Bell Vireo +are no longer than a few feet between adjacent shrubs and trees, +but occasional sustained flights are as long as 300 feet. The birds +fly as low as 2 feet above ground, but have often been observed as +high as 70 feet above the ground.</p> + +<p>In courtship and protracted territorial disputes, where chase between +sexual partners or a pair of antagonists occurs, looping flights +are observed. The wings are beaten as the birds climb and many +aerial maneuvers are performed in the course of the glide.</p> + + +<h4><i>Foraging and Food Habits</i></h4> + +<p>The Bell Vireo has been characterized as a thicket forager (Hamilton, +1958:311; Pitelka and Koestner, 1942:104), but in my experience +it is not restricted to low level strata; birds forage from +ground level upward, both in thickets and isolated trees ranging in +height from 3 feet to 65 feet. The tendency to forage at higher +levels is in part dictated by the presence of tall trees within the +various territories.</p> + +<p>Territories 1 through 7 (1960) contained from three to ten trees +surpassing 40 feet in height. They grew singly or in small groves. +The Bell Vireos foraged fully 20 per cent of the time in these trees. +Food was sought throughout the leaf canopy.</p> + +<p>Behavior in foraging in larger trees followed a routine pattern. +Typically a pair alighted in a tree at a height of 15 feet. Then the +female hopped to a perch a foot above the one upon which she +landed. The male succeeded her to the perch she had previously +occupied. The pair in effect spiraled around some large, essentially +upright, branch, in foraging. The birds usually reached higher +<span class='pagenum'><a name="Page_253" id="Page_253">[Pg 253]</a></span> +perches in this manner rather than by flying upward 10 to 15 feet +to them. This manner of progression within a tree is reminiscent +of a similar habit of the <i>Cyanocitta</i> jays. Presumably, the habit of +the Bell Vireo of foraging in higher strata is facilitated by the absence +of other species of arboreal foraging vireos.</p> + +<p>Chapin (1925:25) found the Bell Vireo to be more insectivorous +in its food habits than any other North American vireo. He found +99.3 per cent of all food contained in 52 stomachs to be of animal +origin. Only three times have I seen a Bell Vireo take food of +vegetable origin. On September 9, 10, and 14, 1959, I noted a male +eating wild cherries over a period of 65 minutes of observation. +Chapin (1925:27) noted that beginning in July vegetable matter +represented 1.57 per cent of the bird's subsistence, and thereafter +slightly more until fall migration.</p> + +<p>Animal food, consisting primarily of insects and spiders, is actively +sought along branches and under leaves. Often a foraging bird will +leap to the underside of a branch and hover, mothlike, beneath a +cluster of leaves while extracting some insect. Some individuals +hung upside down on small branches, paridlike, while foraging. +Lawrence (1953:710), and Southern (1958:201) have recorded +similar behavior of the Red-eyed Vireo. Occasionally, I have seen +a Bell Vireo fly from a perch and capture an insect in the manner +of a flycatcher. The birds do not appear to be adept at this type +of food-getting. Nolan (1960:242) mentions Bell Vireos holding +hard-bodied insects by means of their feet while breaking the +exoskeleton with the beak to obtain the soft parts. Southern (1958:201) +recorded a female Red-eyed Vireo foraging on the ground; I +have seen a Bell Vireo on the ground but once, and it was gathering +nesting material.</p> + + +<h4><i>Bathing</i></h4> + +<p>On May 14, 1960, in a rill that empties into the northeastern edge +of the reservoir a female flew down from a perch six inches above +the surface, barely dipped into the water, flew to a perch 12 inches +above the water, violently shook her ruffled body feathers, quivered +her wings, and rapidly flicked her fanned tail. The entire procedure +was repeated three times in five minutes. She was accompanied by +a singing male that did not bathe.</p> + +<p>Nolan (1960:241) reports a male Bell Vireo bathing by rubbing +against leaves wet with dew; he notes that the White-eyed Vireo +bathes in a similar manner. Southern (1958:201) twice observed +<span class='pagenum'><a name="Page_254" id="Page_254">[Pg 254]</a></span> +Red-eyed Vireos bathing in water that dropped from wet leaves. +In my study area in 1960, only territories 7, 8, 9, and 10 were not +immediately adjacent to permanent water. The pairs of Bell Vireos +in those territories presumably had to reply on wet vegetation for +bathing.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="VOCALIZATIONS" id="VOCALIZATIONS"></a>VOCALIZATIONS</h2> + + +<p>The male Bell Vireo begins to sing regularly soon after its arrival +in spring. Some daily singing continues following the cessation +of breeding activities until departure of the species in late +summer or early fall. The highest sustained rate of song occurs +on the first and second days of nest building. Because careful records +of meteorological data were not kept, I cannot significantly +correlate rates of song and specific temperatures and other weather +conditions. Frequency of song was reduced when the temperature +rose above 90° F., as it did on many days in June, 1960. Nice +(1929:17) mentions a similar decrease in singing when the temperature +exceeded 85° F.</p> + +<p>Passerine birds typically sing at a high rate throughout courtship +and nestbuilding, but at a markedly lower rate thereafter. Most +vireos are atypical in this respect. In the study area in 1960 Bell +Vireos sang more often than Robins, Mockingbirds, Field Sparrows, +Brown Thrashers, Catbirds, and Doves breeding in the same habitat, +about as often as the Meadow Larks in the adjacent fields, and less +often than Painted Buntings.</p> + +<p>The Bell Vireo seems to sing less often in the undisturbed state than +when aware of the presence of an observer. Observations from my car, +at a site approximately equidistant from territories 1 (1960), 2 +(1960), 4 (1960), and 6 (1960) indicate that the rate of song during +incubation is decidedly less when no disturbing influence is present. +Normally, in this period, song aids in maintaining contact between the +members of a pair, serving to locate the male as he forages. Mumford +(1952:230) noted that the males often came out to meet him as he +entered their territories, singing as they approached. The male +typically continues to sing for some time after the intruder has +departed. Here the song acquires the additional functions of alerting +the female to danger and threatening the trespasser. Even after +allowance is made for this reaction to disturbance, Bell Vireos sing +more often than most of their nesting associates, and, on a seasonal +basis, they are vocal for a much longer time.</p> + + +<p><span class='pagenum'><a name="Page_255" id="Page_255">[Pg 255]</a></span></p> +<h4><i>Singing Postures</i></h4> + +<p>In the normal singing posture the body of the Bell Vireo is maintained +at an angle of 35° to the horizontal. Occasionally, during +nest building, I have observed the body held at angles as severe as +80° from the horizontal.</p> + +<p>The head of the White-eyed Vireo is distinctly bobbed up and +down, two or three times, during the utterance of a song phrase. +A bob involves a deliberate withdrawal of the head towards the +body and subsequent sharp, almost vertical, extension of the neck. +The head of the Bell Vireo does not bob, although it vibrates as the +song is delivered.</p> + + +<h4><i>Flight Song</i></h4> + +<p>The Bell Vireo does not have a distinctive flight song; in fact, it +rarely sings or calls while in flight. Nolan (1960:240) has recorded a +male singing the normal song while in flight. Sharp scold-notes are +uttered in mid-air when a bird is agitated or actually attacking an +enemy. These notes and songs recorded by Nolan hardly qualify as +flight song, for this term implies use of a distinctive vocalization +not uttered in other circumstances.</p> + + +<h4><i>Daily Frequency of Song</i></h4> + +<p>In the morning, Bell Vireos usually began singing a few minutes +before sunrise. Their songs were invariably preceded in the study +area by those of Western Kingbirds, Robins, Mourning Doves, +Mockingbirds, Cardinals and Meadow Larks. Bell Vireos sang relatively +little after 6:30 p.m., even on the longest days of the year. +The latest daytime singing that was recorded was seven songs at +7:18 p.m. on June 20, 1960. A Cardinal in the vicinity sang for +a full hour after this.</p> + + +<h4><i>Types of Vocalizations</i></h4> + +<p>Six vocalizations were readily distinguishable in the field. These +are divisible into songs and call notes.</p> + +<p>1. Primary song. It has been described by Pitelka and Koestner +(1942:103) as an "irregular series of harsh and sharp, but slurred +notes preceded by a few distinct notes of the same quality and +ending with a decided ascending or descending note of similar +harshness." The terminal note may also be somewhat abbreviated +and intermediate between an ascending or descending note. The +song is sometimes delivered as a couplet that consists of a phrase +ending on a descending note. This delivery is typical of incubation +and later renesting. During early season activities, the bird utters +<span class='pagenum'><a name="Page_256" id="Page_256">[Pg 256]</a></span> +a phrase ending on the descending note as many as 15 times before +a phrase ending on an ascending note is heard.</p> + +<p>A sonagram of a single phrase, one of several recorded on May +9, 1960 (the third day of building of nest 1-b 1960), consists of +10 notes, the first of which is distinct. The remaining notes are +slurred. This phrase is 1.4 seconds in length.</p> + +<p>Songs are delivered most rapidly in the course of territorial disputes +and defense. The song is loudest in times of nestbuilding and +periods of aggressive behavior. At these times, on clear, calm days, +the songs are audible 100 yards away. Singing in the nestling period +and post-breeding season is audible at distances of no more than +50 feet; such notes have been termed "whisper songs." Table 1 summarizes +singing rates at different periods of the nesting cycle in +several situations and under various weather conditions.</p> + +<p>Songs are of equal frequency in the immediate vicinity of the +nest and elsewhere in the territory. Nice (1929:17) also found this +to be true. Perches can be almost at ground level or as high as 60 +feet. Forty per cent of my data on song concern singing at heights +of more than 20 feet. As indicated in foraging, the lack of competition +from aboreal species of vireos presumably contributes to the use of +higher perches by Bell Vireos.</p> + +<p>No female song was recorded in 1959, but on May 26, 1960, a +female was heard to sing once. She appeared at nest 1-f (1960) +shortly after the male arrived. Unlike him, she did not participate +in building, but seemed to be inspecting the nest. After 30 seconds +she sang once—a low garbled phrase—and also scolded once. After +this she left. In the meantime the continuously singing male moved +two feet away from the nest, then back to it and resumed construction.</p> + +<p>The song of the female signaled to the male her departure. +Pitelka and Koestner (1942:103) heard a female sing twice after +she replaced the male on the nest. Females of three other species +of vireos, the Black-capped Vireo, <i>V. atricapillus</i> (Lloyd, 1887:295), +the Philadelphia Vireo, <i>V. philadelphicus</i> (Lewis, 1921:33), and the +Latimer Vireo, <i>V. latimeri</i> (Spaulding <i>in</i> Pitelka and Koestner, +1942:103) have been heard singing. Lewis and Spaulding also suggest +that the song of the female functions as a signal prior to +exchange at the nest.</p> + +<p>The primary song identifies the singer as a male Bell Vireo. It +aids in securing a mate and in warning potential adversaries; also, +the song is a signal in certain situations and serves to locate the male.<span class='pagenum'><a name="Page_257" id="Page_257">[Pg 257]</a></span></p> + +<h4><span class="smcap">Table 1. Representative Singing Rates of Breeding Bell Vireos. All +Rates Were at Air Temperatures Less Than 86° F. Each Instance Represents +Approximately 30 Minutes of Observation.</span></h4> + + +<table border="1" cellpadding="2" cellspacing="0" summary="Singing Rates"> +<tr> + <th>Circumstance</th> + <th>Instances</th> + <th>Average rate per minute</th> +</tr> +<tr> + <td>Attraction of mate</td> + <td align="center">2</td> + <td align="center">6.3</td> +</tr> +<tr> + <td>Territorial dispute</td> + <td align="center">5</td> + <td align="center">12.8</td> +</tr> +<tr> + <td>Nestbuilding</td> + <td align="center">6</td> + <td align="center">7.0</td> +</tr> +<tr> + <td>Egglaying</td> + <td align="center">1</td> + <td align="center">3.0</td> +</tr> +<tr> + <td>Incubation</td> + <td align="center">6</td> + <td align="center">3.9</td> +</tr> +<tr> + <td>Exchange of partners in the incubation period</td> + <td align="center">1</td> + <td align="center">4.0<a href="#Footnote_A_1" class="fnanchor">[A]</a></td> +</tr> +<tr> + <td>Foraging</td> + <td align="center">2</td> + <td align="center">2.2</td> +</tr> +<tr> + <td>"Morning" song</td> + <td align="center">1</td> + <td align="center">28.6<a href="#Footnote_A_1" class="fnanchor">[A]</a></td> +</tr> +<tr> + <td>"Evening" song</td> + <td align="center">1</td> + <td align="center">1.9<a href="#Footnote_A_1" class="fnanchor">[A]</a></td> +</tr> +<tr> + <td colspan="3" align="right"><b>Overall average rate per minute 6.3</b></td> +</tr> +</table> + +<div class="footnote"><p><a name="Footnote_A_1" id="Footnote_A_1"></a><span class="label">[A]</span> +Not sustained; data representative of periods less than 5 minutes in length.</p></div> + +<p>2. Courtship song. It is here termed the "congested" song and +is comparable to the adult "run-on" song mentioned by Nolan (1960:240). +The congested song is a squeaky version of the primary song +and is given when birds are engaged in pair-formation, nestbuilding, +and egglaying. The delivery is rapid and the sound can be likened +to that made by rapidly scraping a bow across a taut violin string. +Nolan (<i>in</i> Mumford, 1952:230) is probably speaking of this song +when he describes a "tuneless" song that "had a jerky, sputtering +quality that characterizes part of the song of the Ruby-crowned +Kinglet (<i>Regulus calendula</i>)." More recently (1960:240) he applies +the adjectives "twanging," "Bobolink-like," "bubbling," "jerky," and +"squeaky." This song is often blended with the primary song and +is audible for 75 feet.</p> + +<p>A specialized version of the congested song is associated with +pre- and post-copulatory display but differs from the typical squeaky +performance in terminating in two ascending notes reminiscent of the +ascending phrase of the primary song.</p> + +<p>3. Distress call. It was heard only once, when a captured bird +was being freed from a net. When the bird was almost disentangled +it uttered 10 high-pitched, plaintive notes. The quality of the notes +suggested a relationship to the song phrase rather than to other +types of vocalization. A nesting pair of Bell Vireos, 10 feet away, +became extremely excited when they heard the distress notes. They +"scolded" vigorously and flew around my head at a distance of +six feet.<span class='pagenum'><a name="Page_258" id="Page_258">[Pg 258]</a></span></p> + +<p>4. Alarm note. This is a specialized, three-note call of the male +and was heard only from the onset of pair-formation through +early nestbuilding. This whinnying, flickerlike call, phonetically +<i>eh-eH-EH</i>, each succeeding note of which is louder than the one +before, is given whenever the male is disturbed by an unfamiliar +object. This call is generally succeeded by the <i>chee</i>, but occasionally +blends into an extended "whinny," and is typically given from +some perch affording an unobstructed view of the offending object. +The male stretches his neck and cocks his head, the wings and tail +are not flicked or fanned, and no feather tracts are erected. The +bird, nevertheless, flits nervously from perch to perch when uttering +the call.</p> + +<p>5. The <i>zip</i>. The male has a special "scold" note of his own that +is heard when an intruder first approaches the nest. Phonetically +it is <i>zip-zip-zip</i>. It is not so loud as the <i>chee</i>, and the delivery is +more deliberate than that note. If the intruder remains near the +nest, the <i>zip</i> is usually replaced by the <i>chee</i>.</p> + +<p>6. The generalized call note or <i>chee</i>. The call notes associated with +several situations are combined under this subheading since all can be +rendered in English by the same phonetic equivalent—<i>chee</i>. The +<i>chee</i> associated with nestbuilding is of moderate pitch and delivered +deliberately at a rate of about 40 per minute. The feeding call of the +adults is a soft slurred <i>chee</i>, while that of the nestlings has a +mewing quality. In general, the <i>chee</i> utilized in signal situations +consists of a few repetitions of the basic note emitted at a moderate +pitch. The <i>chee</i> associated with hostile and courtship behavior is +higher pitched and the delivery is much more rapid, approximately 200 +per minute. Nolan (1960:240) reports a continuous rate of 25 per five +seconds when an adult Bell Vireo is alarmed. The <i>chee</i> of extreme +anxiety is a loud emphatic buzz, phonetically ZZ-ZZ-ZZ-ZZ.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="TERRITORIALITY" id="TERRITORIALITY"></a>TERRITORIALITY</h2> + + +<p>The Bell Vireo exhibits "classic" passerine territoriality. Within +a specific area, a pair of this species carries out pair-formation, +courtship activities, copulation, nesting, rearing the young, and +foraging. With the cessation of reproductive activities, a pair continues +to restrict its other daily activities to the same general area.</p> + +<p><span class='pagenum'><a name="Page_259" id="Page_259">[Pg 259]</a></span></p> +<h4><i>Establishment of Territory</i></h4> + +<p>In early May the segment of the total suitable habitat within +which a Bell Vireo restricts its activities is not rigidly defined and +the first male of the season ranges over an area too large to be +maintained permanently—one that seems greatly to exceed the +needs of breeding. Male 1 (1960), for instance, was first seen foraging +over an area of approximately seven acres. With the influx +of other males, portions of this large tract were usurped and the +territory of the original male was gradually reduced to an area +of little more than an acre.</p> + +<p>In this initial period, a male becomes identified with a large area +but is restricted to an area of nearly typical size by the +encroachment of other males. Territorial disputes in this period often +involve physical contact, as well as protracted sessions of +high-intensity singing at rates exceeding three hundred song-phrases +per hour.</p> + +<p>Eventually the carrying capacity of the habitat is reached and +no further partitioning occurs. The beginning of nestbuilding +coincides with this relative stabilization of the territorial boundaries. +Through the remainder of the cycle of behavior associated with any +one nest, all activity is that of the occupant pair within its territory.</p> + + +<h4><i>Size of Territories</i></h4> + +<p>The nine original territories established in 1960 varied in size from +0.26 acre to 3.1 acres (Table 2). Fitch (1958:270) found the +territories of several pairs of Bell Vireos at the University of +Kansas Natural History Reservation to vary from 0.4 to 1 acre. Hensley +(1950:243) estimated the size of the territory of a pair of Bell +Vireos observed in Piatt County, Illinois, at 3.1 acres. Nolan +(1960:227) records home ranges of 2 to 3 acres. The pairs that he +studied were sole occupants of fields several acres larger than the +portions actually utilized. His description of the vegetation +indicates that most of the second growth was not much taller than 7 +feet. As indicated elsewhere, the second-growth in my tract averaged +15 feet tall. The smaller average size of territory (1.25 acres) that +I found is probably a function both of this greater vertical range of +available foraging area and the much higher gross density of birds (40 +pairs per 100 acres).</p> + + +<p><span class='pagenum'><a name="Page_260" id="Page_260">[Pg 260]</a></span></p> +<h4><i>Permanence of Territories</i></h4> + +<p>Most pairs remain in their original territories throughout the +summer, although some shift certain territorial boundaries. In +1960 pairs 2 and 6, in the course of selecting a site for a replacement +nest, annexed adjacent areas previously occupied by other +pairs. Pair 2 relocated in a space that originally included territories +1 and 4, and pair 6 built a nest in an area formerly occupied by +pair 7. Males 1 and 4 were sacrificed for specimens and pair 7 +probably was destroyed by a predator. Owing to the presence of +a nest, the annexed area becomes the focal point of the activities +of a pair, but the original area is regularly visited and may be returned +to in a later renesting.</p> + +<h4><span class="smcap">Table 2. Size of the Nine Original Territories Occupied in 1960.</span></h4> + +<table border="1" cellpadding="2" cellspacing="0" summary="Singing Rates"> +<tr> + <th>Territory</th> + <th>Date first occupied</th> + <th>Dimensions</th> +</tr> +<tr> + <td>1.</td> + <td>May 3, 1960</td> + <td align="right">1.6 acres</td> +</tr> +<tr> + <td>2.</td> + <td>May 5, 1960</td> + <td align="right">0.6 acre</td> +</tr> +<tr> + <td>3.</td> + <td>May 7, 1960</td> + <td align="right">0.26 acre</td> +</tr> +<tr> + <td>4.</td> + <td>May 11, 1960</td> + <td align="right">1.03 acres</td> +</tr> +<tr> + <td>5.</td> + <td>May 12, 1960</td> + <td align="right">2.07 acres</td> +</tr> +<tr> + <td>6.</td> + <td>May 14, 1960</td> + <td align="right">3.1 acres</td> +</tr> +<tr> + <td>7.</td> + <td>May 13, 1960</td> + <td align="right">1.7 acres</td> +</tr> +<tr> + <td>8.</td> + <td>May 14, 1960</td> + <td align="right">0.46 acre</td> +</tr> +<tr> + <td>9.</td> + <td>May 14, 1960</td> + <td align="right">0.4 acre</td> +</tr> +<tr> + <td colspan="3" align="right"><b>Average 1.25 acres</b></td> +</tr> +</table> + + +<h4><i>Maintenance of Territory</i></h4> + +<p>Except in the early stages of nesting, territory is maintained +primarily by song. In the period of incubation a male regularly +patrols his territory between sessions of sitting on the eggs. He +sings several songs from each of several perches. A male follows +a predictable path, rarely traveling more than 150 feet from the +nest. Incipient patrolling is seen early in the breeding season +when territorial boundaries are in a state of flux.</p> + +<p>The male White-eyed Vireo travels a semi-predictable route, as does +the Solitary Vireo (R. F. Johnston, MS). According to Lawrence +(1953:50), the male Red-eyed Vireo has a distinct singing area +completely divorced from the nest area dominated by the female. +Southern (1958:109), working with this same species in Michigan, did +not recognize separate areas, but found that the male wandered +randomly over the territory.</p> + +<p><span class='pagenum'><a name="Page_261" id="Page_261">[Pg 261]</a></span> +In a species so highly active as the Bell Vireo, the degrees of +hostile action associated with an encounter overlap in such a +fashion that no clearcut distinction can be drawn among the various +displays. Nevertheless, certain generalized patterns are characteristic +of all situations in which members of this species are in a state +of anxiety. The threat displays described in the succeeding paragraphs +may all be utilized within as little as two minutes; mutual +agonism may be terminated at any stage by concerted attack of the +dominant bird.</p> + +<p>1. Vocal threat. When an intruder is discovered the resident +male markedly increases his rate of singing. The alarm note, <i>eh-eH-EH</i>, +is the first call uttered during the nestbuilding and egglaying +periods.</p> + +<p>2. Head-forward threat. If the intruder does not flee, the resident +male adopts a specific threat posture. The head and neck +are extended. The feathers of the crown are erected, but those of +the body are sleeked. The bird crouches slightly and the tail is +flicked laterally, but not fanned. The intensity of the singing increases +and is supplemented by scolding, also delivered at a rapid +rate. The intruder normally retreats at this juncture.</p> + +<p>3. Wing-flicking and submaximal tail-fanning. If the interloper +remains, the anxiety of the resident male increases. He slightly +depresses the tail and, at the same time, rapidly fans and closes it. +The tail is only partially fanned. The wings are held slightly away +from the body and rapidly flicked above the back. This flicking +should not be confused with quivering of the wings associated with +begging and other solicitory postures. Song is now almost completely +replaced by high-intensity scolding. Associated with this +high degree of anxiety are displacement behaviorisms, including +bill-wiping, reversal of direction on a single perch, and a nervous +hopping from one perch to another.</p> + +<p>4. Ruffling and maximum tail-fanning. This display is most +often seen in conjunction with the harassment of predators, but +occasionally it is observed in territorial disputes occurring at the +boundary of adjacent territories where neither male is strictly +dominant and in which there is much vacillation prior to attack. +The feathers of the abdomen are ruffled. The term "ruffled" pertains +to a full erection of the feathers, giving a ragged appearance +to the body outline (Morris, 1956:80). Ruffling of the abdominal +feathers emphasizes their yellow color and seemingly heightens +the intimidatory effect. The tail is fully fanned, and so maintained, +<span class='pagenum'><a name="Page_262" id="Page_262">[Pg 262]</a></span> +for a few seconds at a time; it is held at a 45° angle to the body. +The scold becomes an extremely intense, stacatto buzz, ZZ-ZZ-ZZ-ZZ.</p> + +<p>5. Supplanting attack. The attack directed against a trespassing +male is initiated as a lunge that results in a collision with the opponent +in mid-air or on his perch. The bird attacked is struck by +his adversary's open beak or body.</p> + +<p>Hinde (1952:71-72) indicates four courses of action followed by a +Great Tit (<i>Parus major</i>) when attacked under similar circumstances. +"(a) It flies away: The attacker usually flies after it and +a chase ensues. (b) It shifts its perch a few inches: the attacker +lands in its place, and both usually show head-up postures. (c) +It remains where it is, but adopts a head-up posture: the attacker +usually then shows upright flight. (d) It may fly up and meet +the attacker in mid-air: in that case an actual combat may result, +or both combatants may show upright flight."</p> + +<p>Head-up posturing and upright flight are not presently recognized +components of the behavior of the Bell Vireo. The behavior of the +attacked Bell Vireo is similar to that described in (a), (b), and +(d) above, and is clearly dictated by the proximity of his own +"home base."</p> + +<p>Eleven disputes among occupants of adjacent territories were +witnessed between May 6 and June 3, 1960, in which some or all +of the described threat displays were manifest (Table 3). In each +instance, patrolling males were gradually attracted to each other. +As they approached, their rates of song increased from an average of +six repetitions per minute to 15 per minute. Eight of the disputes +involved physical combat.</p> + +<p>On May 6, 1960, when male 2 (1960) was in the process of usurping +an eastern segment of the original territory of male 1 (1960), +a violent, protracted dispute was observed. By this date male 1 +(1960) had obtained a mate and had begun construction of nest +1-a (1960); male 2 (1960) had not yet acquired a mate. At first +the two males were singing vigorously, from one to 10 feet apart. +Female 1 (1960) followed her mate closely and scolded, at the same +time partially fanning her tail. In the course of vocal dueling the +males had traveled to within 50 feet of nest 1-a (1960), when male 1 +(1960) suddenly lunged at 2 (1960). The males plunged to the +ground, locking bills and clutching at each other with their feet as +they fell. As soon as they touched the ground they separated. +<span class='pagenum'><a name="Page_263" id="Page_263">[Pg 263]</a></span> +Male 2 flew east with male 1 in pursuit. This conflict lasted three +minutes.</p> + +<p>Additional physical combat was witnessed several minutes later. +This again involved striking with the bill, wings and feet. A high +pitched squeaky <i>chee</i> was uttered by both combatants. The female +scolded from a nearby perch. Upon separating, the males engaged +in a wild, looping flight. At about 350 feet from nest 1-a (1960), +the chase abruptly ended. For ten minutes thereafter, both males +sang at a high rate from perches about 10 feet apart. This terminated +the physical combat, but three additional protracted, vocal +duels occurred in the remainder of the morning.</p> + +<h4><span class="smcap">Table 3. Intraspecific Disputes in Maintenance of Territory.</span></h4> + +<h4>Behavior</h4> + +<table border="1" cellpadding="2" cellspacing="0" summary="Maintenance of Territory"> +<tr> + <th> </th> + <th>Number of conflicts</th> + <th>Vocal dueling</th> + <th>Combat</th> + <th>Average length of disputes</th> +</tr> +<tr> + <td>Prenesting</td> + <td align="center">3</td> + <td align="center">3</td> + <td align="center">2</td> + <td>6 min. 40 sec.</td> +</tr> +<tr> + <td>Building</td> + <td align="center">8</td> + <td align="center">8</td> + <td align="center">6</td> + <td>3 min. 8 sec.</td> +</tr> +<tr> + <td>Incubation</td> + <td align="center">1<a name="FNanchor_A_2" id="FNanchor_A_2"></a><a href="#Footnote_A_2" class="fnanchor">[B]</a></td> + <td align="center">1</td> + <td align="center">...</td> + <td>20 min.</td> +</tr> +<tr> + <td><b>Totals</b></td> + <td align="center"><b>12</b></td> + <td align="center"><b>12</b></td> + <td align="center"><b>8</b></td> + <td><b>5 min. 30 sec.</b></td> +</tr> +</table> + +<div class="footnote"><p><a name="Footnote_A_2" id="Footnote_A_2"></a><a href="#FNanchor_A_2"><span class="label">[B]</span></a> +Directed against a stuffed Bell Vireo.</p></div> + +<p>Probably as a direct result of these conflicts, a neutral zone +approximately 300 feet wide developed between the two territories. By +May 14 this intervening area was occupied by male 4 (1960). By this +date both 1 (1960) and 2 (1960) were involved in nestbuilding and 4 +(1960) was not challenged for several days.</p> + +<p>Maximum tail-fanning prior to attack also appears as an element +of aggressive behavior in White-eyed Vireos. A brief skirmish between +a male of this species and a small, greenish passerine was +observed at the Natural History Reservation on May 25, 1960. The +White-eyed Vireo was singing from a perch 30 feet high in a dead +elm, when the unidentified passerine landed 10 feet distant. The +white-eye ceased regular song and uttered several catbirdlike calls, +and at the same time slightly depressed and fully fanned the tail. +After 10 seconds, the white-eye lunged at the intruder, striking it in +mid-air. A brief looping flight ensued through the branches of the +elm before the intruder was able effectively to retreat.</p> + + +<p><span class='pagenum'><a name="Page_264" id="Page_264">[Pg 264]</a></span></p> +<h4><i>Aggressive Behavior of the Female</i></h4> + +<p>The female Bell Vireo is concerned primarily with the defense of +the nest and the young and she rarely assists the male in defense +of distant parts of the territory. She employs the same threat displays +as the male.</p> + + +<h4><i>Interspecific Relationships</i></h4> + +<p>A number of meetings between Bell Vireos and other species were +observed in the course of the study (Table 4). Resident pairs of +this species exhibited different degrees of tolerance toward other +species. Many birds, including Cardinals, Field Sparrows, Painted +Buntings and Mourning Doves were ignored completely. Chickadees +evoked responses characterized by slight increase in song and +some anxiety; this was perhaps owing to similarity in size, motion +and call notes. Warblers, when met with, were invariably chased. +They may be momentarily mistaken for rival vireos.</p> + +<h4><span class="smcap">Table 4. Interspecific Conflict Observed in 1959 and 1960.</span></h4> + +<table border="1" cellpadding="2" cellspacing="0" summary="Interspecific Conflict"> +<tr> + <th rowspan="2">Species</th> + <th rowspan="2">Number of conflicts</th> + <th rowspan="2">Phase of breeding cycle</th> + <th colspan="4">Behavior of Bell Vireos</th> +</tr> +<tr> + <th>HFT<a name="FNanchor_A_3" id="FNanchor_A_3"></a><a href="#Footnote_A_3" class="fnanchor">[C]</a></th> + <th>S</th> + <th>TF</th> + <th>A</th> +</tr> +<tr> + <td><i>Coccyzus americanus</i></td> + <td>1</td> + <td>Nestling period</td> + <td> </td> + <td>x</td> + <td> </td> + <td> </td> +</tr> +<tr> + <td><i>Cyanocitta cristata</i></td> + <td>3<a name="FNanchor_B_4" id="FNanchor_B_4"></a><a href="#Footnote_B_4" class="fnanchor">[D]</a></td> + <td>Nestling and incubation period</td> + <td>x</td> + <td>x</td> + <td>x</td> + <td>x</td> +</tr> +<tr> + <td><i>Parus atricapillus</i></td> + <td>1</td> + <td>Prenesting</td> + <td> </td> + <td>x</td> + <td> </td> + <td> </td> +</tr> +<tr> + <td><i>Molothrus ater</i></td> + <td>1</td> + <td>Nestling period</td> + <td> </td> + <td>x</td> + <td> </td> + <td>x</td> +</tr> +<tr> + <td><i>Dendroica petechia</i></td> + <td>1</td> + <td>Prenesting</td> + <td> </td> + <td>x</td> + <td> </td> + <td>x</td> +</tr> +<tr> + <td><i>Geothlypis trichas</i></td> + <td>1</td> + <td>Nestbuilding</td> + <td> </td> + <td>x</td> + <td> </td> + <td>x</td> +</tr> +<tr> + <td><i>Pituophis catenifer</i><a name="FNanchor_C_5" id="FNanchor_C_5"></a><a href="#Footnote_C_5" class="fnanchor">[E]</a></td> + <td>1</td> + <td>Post-fledging</td> + <td> </td> + <td>x</td> + <td> </td> + <td>x</td> +</tr> +</table> + +<div class="footnote"><p><a name="Footnote_A_3" id="Footnote_A_3"></a><a href="#FNanchor_A_3"><span class="label">[C]</span></a> +HFT = head-forward threat; S = scolding; TF = tail-fanning; A = attack.</p></div> + +<div class="footnote"><p><a name="Footnote_B_4" id="Footnote_B_4"></a><a href="#FNanchor_B_4"><span class="label">[D]</span></a> +Includes attack against a dummy Blue Jay.</p></div> + +<div class="footnote"><p><a name="Footnote_C_5" id="Footnote_C_5"></a><a href="#FNanchor_C_5"><span class="label">[E]</span></a> +The Bull Snake is here included because the vireos directed typical aggressive displays towards it.</p></div> + +<p>Blue Jays were vigorously attacked, especially late in incubation +and throughout the nestling period of the Bell Vireo. I did not see +a jay struck, but a vireo would circle one closely as it perched and +pursue it when it flew, following as far as 100 yards beyond territorial +bounds. The buzz, ZZ-ZZ-ZZ-ZZ, was uttered in conjunction +with this harassment.</p> + +<p>A stuffed jay placed eight feet from a nest elicited threat display +and displacement behavior from the owners of the nest, but no +<span class='pagenum'><a name="Page_265" id="Page_265">[Pg 265]</a></span> +attack. Incubation had just begun at this nest. A dummy Bell Vireo +placed close to another nest only momentarily disturbed the male, +and the female completely ignored it. Incubation had also recently +begun at this nest. At this same general stage, moreover, nesting +pairs showed little inclination to harass me.</p> + + +<h4><i>Discussion</i></h4> + +<p>Hinde (1956:341-342) indicates that territory has been defined +in a number of ways by many workers. All of the definitions involve +modification of Howard's classic "defended area." Pitelka (1959:253) +has reacted against this behaviorally-oriented concept. He +thinks that the concept of territory should be based on exclusive +use of an area by its occupants, and not so much the defense by +which they maintain it.</p> + +<p>Methods of treating territoriality in the Bell Vireo seemingly +incorporate features of both schools of thought. The area used +exclusively for all biological needs by a single pair of Bell Vireos +is vigorously defended both physically and vocally early in the +breeding season and vocally as the season progresses.</p> + +<p>In the period of territorial establishment a relatively large area +is actively defended. The building of a nest establishes a focal point +of activity in a somewhat more restricted area than that originally +occupied. After the success or failure of a nest, a new site is selected +to which the focal point of activity is shifted. If suitable habitat +adjacent to the extant territory is unoccupied by other Bell Vireos +the unoccupied area may be annexed in the course of searching for +a new site. Such annexation occurs only when pairs formerly occupying +adjacent suitable habitat disappear from this territory; +possibly the size of the territory of any one pair is dictated by the +density of population of the species as well as by the presence of +suitable habitat. This may not always be true as indicated by +Kliujver (1951:40), who in studying the Great Tit, found no appreciable +difference in the size of territory in two different habitats +even though there was a marked difference in population density +of the birds.</p> + +<p>Fluctuation of territorial boundaries is not uncommon in passerines, +especially when no rivals exist to contest movement. Hinde +(1956:351) indicates that fluctuations in size of territory are to be +expected although the territories of different species of birds have +different mean sizes.</p> + +<p>Once nesting activities commence there is a marked reduction in +<span class='pagenum'><a name="Page_266" id="Page_266">[Pg 266]</a></span> +the amount of territory utilized and a distinct decrease in the +aggressive tendencies of the male; it would seem that energy previously +utilized in regular fighting is rechanneled for nestbuilding, +incubation and care of the young. Further, contraction of the area +of activity obviates high-intensity territorial defense, as adjacent +males, even in regions of high population density, are isolated from +one another by an area no longer regularly traversed.</p> + +<p>With cessation of breeding activities physiological mechanisms +governing maintenance of territory seemingly are no longer active +and yet the pairs of Bell Vireos remain within a restricted area which +they alone use. Earlier definitions of territory as a "defended area" +do not adequately cover such situations and yet from the standpoint +of Pitelka the area still retains the characteristics of true territory. +In fact, territory as defined by Pitelka is clearly manifest at this +time. Whether the birds remain in an area through "force of habit" +is of little consequence.</p> + +<p>I have retained the term "territory" in preference to the term +"home range" used by Nolan (1960:227). His failure to observe +territorial defense is responsible for his terminology, although it is +readily understandable that such defense would be lacking in a +population of relatively low density in which pairs were isolated +from one another by areas of unfavorable habitat. This isolation in +itself would tend to preclude territorial conflict but territories were, +in fact, maintained.</p> + +<p>The marked similarity in the essential features of aggressive +behavior in North American vireos attests to their close relationship. +Flicking and fanning of the tail are distinct components of the hostile +behavior of the Bell Vireo, White-eyed Vireo, Red-eyed Vireo (Lawrence, +1953:69), and the Black-whiskered Vireo (<i>Vireo altiloquus</i>; +Bent, 1950:319), and, presumably, of the remaining species of the +genus. The occurrence of these same displays as intrinsic behavioral +elements of interspecific hostility suggests a common derivation. +Moynihan (1955:256) indicates that all intraspecific hostile displays, +and probably most interspecific hostile displays, evolved originally +as social signals having the same general function. Further, Hinde +(1956:344) points out that there is a fundamental similarity in the +motor patterns used in fighting in different contexts, including both +interspecific and intraspecific fighting.</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_267" id="Page_267">[Pg 267]</a></span></p> +<h2><a name="COURTSHIP_BEHAVIOR" id="COURTSHIP_BEHAVIOR"></a>COURTSHIP BEHAVIOR</h2> + + +<p>The precise mechanism of pair-formation in the Bell Vireo is not +known. My experience has been to find a male one day and then +one or two days later to discover that it has a mate. Lawrence +(1953:53), tells of a male Red-eyed Vireo singling out a female +from a flock of migrants passing through his territory and violently +driving her to the ground. Shortly after this attack the pair was +seen searching for a nest site. But such an incident has not been +reported for other vireos, nor have I witnessed such behavior myself.</p> + +<p>Early courtship activities of the Bell Vireo are characteristically +violent affairs, with the male directing strong aggressive attacks +toward the female. Rapid, looping flights through the thickets +occur, the female leading the male. Occasionally he deliberately +collides with her in mid-air, but the pair quickly separate. This +violent sexual chasing is manifest prior to the inception of nestbuilding. +With commencement of this activity, sexual chases through +the territory subside.</p> + +<p>Absence of sexual dimorphism in the Bell Vireo obviously suggests that +behavioral criteria are used by the birds in sex-recognition. The lack +of aggression by the female upon initial aggression by the male is an +essential component of recognition of sex; she is clearly subordinate. +Such subordination is also the significant feature of continued +sex-recognition. Courtship display by a resident male, directed toward +a stuffed male and a wounded male which sat motionless, supports the +contention that a subordinate or submissive attitude of the female is +a key factor in sex-determination.</p> + +<p>Nestbuilding and courtship are intimately associated in this +species. The male constructs the suspension apparatus of the nest, +the completion of which coincides with the assumption of nestbuilding +activity by the female. Roles of the sexes in nestbuilding are +described in the section on nestbuilding. The male frequently interrupts +construction to court the female. This, in combination with +perpetual song as he works, serves to strengthen the pair-bond and +stimulate nestbuilding tendencies of the female.</p> + +<p>It is doubtful that any attempts at copulation are successful up +to this time. The female is singularly unresponsive to the advances +of the male; a female retreats before most violent attacks and is +seemingly oblivious to less vigorous behavior. After the female +<span class='pagenum'><a name="Page_268" id="Page_268">[Pg 268]</a></span> +assumes the responsibility of building, the tempo of courtship +activities increases.</p> + +<p>The female becomes increasingly more receptive and her work is +often interrupted by advances of the male. Copulation occurs frequently +from about the third day of nestbuilding through the first +day of egglaying, a period of four to six days. Male displays and +vocalizations associated with courtship continue through the fourth +or fifth day of incubation.</p> + + +<h4><i>Displays and Postures</i></h4> + +<p>The principal courtship displays and postures that were seen +throughout the nestbuilding phase are as follows:</p> + +<p>1. Greeting ceremonies. Both birds are crouched from one to five +inches apart. The feathers on one (the male?) are sleeked, and on +the other are fluffed. Fluffing (Morris, 1956:80) denotes partial +erection of the body feathers producing a rounded, unbroken body +line and is not to be confused with ruffling, mentioned in the sections +pertaining to territoriality and pre- and post-copulatory display. +Fluffing is generally considered to be an appeasement display and +it is seen in a variety of situations involving a dominant-subordinate +relationship. Both birds flick wings and tails rapidly and reverse +directions on their perches frequently. A low, rapid <i>chee</i> is uttered +during this performance. This ceremony is repeated often in the +first three days of nestbuilding, but less frequently thereafter. It +usually occurs after building by one or both partners and prior to +another trip in search of nesting material. It lasts from 10 to 50 +seconds and is not immediately followed by any additional courtship +activities. Nolan (1960:228-229) observed mutual displays between +periods of violent sexual chase that suggest that the greeting ceremonies +that I have described are an integral part of pair-formation +as well as a component of continued maintenance of the bond.</p> + +<p>2. "Pouncing." The female rapidly quarter-fans and partially +depresses her tail. She utters a high pitched scold (<i>chee</i>). The +male, from a perch within two feet of the female, fans the tail fully +and depresses it vertically, and, with mouth open, lunges at the +female; or, with similar tail mannerisms, the abdominal feathers +ruffled, the wings held horizontally, and the primaries spread, he +sways from side to side from four to six times, and then lunges at +the female. The male is silent when he pounces; the <i>chee</i> or the +courtship song is emitted when swaying precedes pouncing. The +male strikes the female with his breast or with his open beak. The +female rarely flees although she is usually displaced several inches +<span class='pagenum'><a name="Page_269" id="Page_269">[Pg 269]</a></span> +along the branch upon which she is sitting. However, the female +may fly several inches to a new perch. The failure of the female to +adopt a solicitation posture presumably indicates sexual unreadiness. +Instances of the male deliberately colliding with the female +as she flies in the course of gathering nesting material are probably +analogous to pouncing. In none of the above situations are females +observed to fight back in any way. Nice (1943:174) believed pouncing +to be analogous to sexual chasing found in such species as the +Red-winged Blackbird. In the Song Sparrow, pouncing is observed +most often in the first and second days of nestbuilding.</p> + +<p>3. "Leap-flutter." The male, in the course of displaying with the +tail fanned before the female, suddenly leaps eight inches to ten +inches vertically and flutters in mid-air several seconds, before dropping +to the original perch. This display occurs in full view of the +female. It is often associated with pouncing and is also seen prior +to copulation. In the latter instance it is probably pragmatically +functional, for it permits the male to orient above the female before +dropping to her back to copulate. No vocalization is uttered during +the leap-flutter.</p> + +<div class="figcenter" style="width: 70%;"> +<img src="images/i031.jpg" width="100%" alt="Fig. 3." title="Fig. 3." /> +<span class="caption"><span class="smcap">Fig. 3.</span> A single male Bell Vireo +in the pre-copulatory display. Note the ruffled dorsal and ventral body feathers. +The male on the left has reached the zenith of a single swing. The male on the +right has nearly reached the low point of a swing.</span> +</div> + +<p>4. Pre-copulatory display (Fig. 3). The male faces the female. +The tail is fanned fully and depressed at a sharp vertical angle to +the body. Body feathers, both dorsal and ventral, are ruffled, almost +tripling the apparent volume of the thorax. The head is withdrawn +and slightly thrown back. Feathers of the head are not erected. +<span class='pagenum'><a name="Page_270" id="Page_270">[Pg 270]</a></span> +The mouth is opened wide. The legs are slightly flexed and the +body is swayed laterally. Horizontally, the head and body traverse +an arc of about 100°; vertically, they traverse an arc slightly less +than 180°. At the low point of any one swing, the delivery of the +courtship song begins. At the termination of the swing the two +normal, ascending notes are emitted. This performance may last +as long as three minutes.</p> + +<p>The pre-copulatory display of the male elicits receptive behavior +in the female. She crouches in a solicitous manner, with the body +feathers fluffed and the tail raised slightly, and utters a muted <i>chee</i>.</p> + +<p>5. Copulation. The male abruptly terminates his swaying display +with a leap-flutter that positions him above the female's back. He +then descends and copulation occurs. The male continues to flutter +his wings to maintain balance throughout the two seconds of cloacal +contact. Following an unsuccessful copulation on June 23, 1960, +displacement preening and bill wiping were performed by both +sexes.</p> + +<p>6. Post-copulatory display. On June 25, 1960, after a second +attempt at copulation with a stuffed bird in which semen was +actually deposited on the dummy's back, male 10 (1960) performed +a swaying display. In this instance, however, instead of addressing +the dummy from the front, the male alighted one inch to the right +of the stuffed bird. When swaying to the left (toward the dummy) +the head of the displaying male actually passed above the neck of +the stuffed bird. This ritualized behavior could conceivably be +derived from hetero-preening.</p> + + +<h4><i>Discussion</i></h4> + +<p>Within the scope of my research it was difficult to detect the +over-all sequence of epigamic displays that result in synchronization +of the physiological states of the sexes throughout the period of +courtship. Possibly all displays, except the post-copulatory one, +occur in no particular order in the courtship period. However, each +ritualized display seemingly strengthens the pair-bond.</p> + +<p>Swaying has been recorded in a variety of situations of a sexual +and semi-sexual nature for the Solitary Vireo (<i>V. solitarius</i>; Townsend, +1920:158) and the Red-eyed Vireo (Tyler, 1912:230; Bent, +1950:342). In every instance the body feathers of the swaying +birds were sleeked. Courtship behavior in any species of North +American vireo seems closely to resemble that of any other; pairing +<span class='pagenum'><a name="Page_271" id="Page_271">[Pg 271]</a></span> +and nestbuilding of a female <i>V. solitarius</i> and a male <i>V. flavifrons</i> +as reported by Hauser (1959:383) support the idea of close resemblance.</p> + +<p>A marked similarity will be detected between certain basic elements +of aggressive and epigamic displays. These basic elements +are wing- and tail-flicking, tail-fanning, and high-intensity delivery +of the <i>chee</i>. Pouncing and supplanting attacks are essentially similar. +Such similarities suggest either a common origin for certain +aggressive and epigamic displays or the derivation of one from the +other.</p> + +<p>High-intensity <i>cheeing</i> is obviously a function of excitement, +whether in conjunction with hostility or sexual behavior. According to +Andrew (1956:179), flicking of wing and tail in passerines are +intention movements of flight. These actions have been emancipated +from incomplete take-offs and incorporated in ritualized courtship and +agonistic behavior. In incipient courtship behavior the male is +governed by three conflicting tendencies; to flee, to attack, or to +behave sexually before his mate (Tinbergen and Hinde, 1958:256). When +pairing, Bell Vireos interrupt sexual chase with "greeting +ceremonies," the male's tendency to attack and the female's tendency +to flee are momentarily reduced, and the forming bond is strengthened. +Thus, the intention movements become an integral part of courtship.</p> + +<p>In situations where attacking and fleeing are the two conflicting +tendencies, wing-flicking and tail-flicking are incorporated into +threat display, but do not lose all of their original function, for +they facilitate attack. Tail-fanning, as a display element, increases +the awesome aspect of the threatening bird and in courtship presumably +makes the sexes more attractive to one another.</p> + +<p>Courtship feeding has not been recorded for the Bell Vireo. In +general, it is unknown in North American vireos, with the exception +of the red-eye (Lawrence, 1953:53). It would serve no "practical" +purpose in the Bell Vireo since the male regularly relieves the +female during incubation, thus allowing her ample opportunity to +forage. In the Red-eyed Vireo, only the female regularly incubates, +and courtship feeding is definitely functional. Nolan (1960:228) +described a brief pecking or pulling with their bills between +pairing birds. This may be incipient "symbolic" courtship feeding, +or perhaps mutual preening.</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_272" id="Page_272">[Pg 272]</a></span></p> +<h2><a name="SELECTION_OF_NEST-SITE_AND_NESTBUILDING" id="SELECTION_OF_NEST-SITE_AND_NESTBUILDING"></a>SELECTION OF NEST-SITE AND NESTBUILDING</h2> + + +<p>As far as can be determined, the nest-site is selected by the +female. Typically, the pair makes short, low-level flights from tree +to tree with the female invariably in the lead. The birds usually +forage within each tree; the female interrupts this activity to inspect +small forks of low, pendant branches and the male occasionally +pauses to sing. The singing is loud but not particularly regular, +as it is later when the male accompanies the female during actual +nestbuilding. Method of selection of site resembles that described +by Lawrence (1953:53) for the Red-eyed Vireo.</p> + +<p>Nests are suspended from lateral or terminal forks about 27 inches +high in bushes and small trees that, in the study area, averaged +11 feet, four inches in height (Table 5). The height above ground +of the nests does not vary appreciably as the season progresses as +is the case with nests of Red-eyed Vireos, for which Lawrence +(1953:54) noted that late nests were placed higher than those +built earlier in the season.</p> + +<p>Most nests are so situated that they are protected and concealed +by the dense foliage of trees. Where nests are placed in low bushes, +as coralberry or dogwood, the bush is invariably overhung by the +foliage of a much taller shrub or tree.</p> + +<p>The nest tree or shrub was in every instance situated at the edge +of a thicket or isolated from adjacent trees by several feet. Preference +for open situations is characteristic of the species. In contrast, +the nest of the White-eyed Vireo (Bent, 1950:229) is placed +toward the center of thickets.</p> + +<p>In the choice of sites in the study area, the Bell Vireos were +almost unopposed by other avian species, owing to the size of the +<span class='pagenum'><a name="Page_273" id="Page_273">[Pg 273]</a></span> +fork utilized and the fact that the nests are located peripherally, +rather than centrally, in the bush or tree. This lack of competition +for a nest-site provides a Bell Vireo with an ample supply of nest-sites +within any one territory.</p> + +<h4><span class="smcap">Table 5. Nest-sites Utilized in 1960.</span></h4> + +<table border="1" cellpadding="2" cellspacing="0" summary="Nest-sites Utilized"> +<tr> + <th>Plant</th> + <th>Number of nests</th> + <th>Average height of plant</th> + <th>Average height of nest</th> +</tr> +<tr> + <td><i>Ulmus americana</i></td> + <td align="center">4</td> + <td>7 ft. 6 in.</td> + <td>2 ft. 3 in.</td> +</tr> +<tr> + <td><i>Maclura pomifera</i></td> + <td align="center">20</td> + <td>13 ft. 11 in.</td> + <td>1 ft. 11 in.</td> +</tr> +<tr> + <td><i>Crataegus mollis</i></td> + <td align="center">1</td> + <td>11 ft.</td> + <td>3 ft. 1 in.</td> +</tr> +<tr> + <td><i>Gleditsia triacanthos</i></td> + <td align="center">2</td> + <td>15 ft. 6 in.</td> + <td>1 ft. 9 in.</td> +</tr> +<tr> + <td><i>Acer negundo</i></td> + <td align="center">4</td> + <td>8 ft. 9 in.</td> + <td>2 ft. 5 in.</td> +</tr> +<tr> + <td><i>Cornus drummondi</i></td> + <td align="center">2</td> + <td>8 ft.</td> + <td>2 ft. 8 in.</td> +</tr> +<tr> + <td><i>Symphoricarpos orbiculatus</i></td> + <td align="center">3</td> + <td>3 ft.</td> + <td>1 ft. 10 in.</td> +</tr> +<tr> + <td><b>7</b></td> + <td align="center"><b>36</b></td> + <td><b>11 ft. 4 in.</b></td> + <td><b>2 ft. 3 in.</b></td> +</tr> +</table> + +<p>Selection of the first nest-site may take as long as two days, +possibly owing to incomplete development of the nesting tendency, +but more likely to a general lack of familiarity with the territory. +Red-eyed Vireos require five to six days to choose the first nest-site +(Lawrence, 1953:54). Later sites of the Bell Vireo are chosen in +as little as three hours. Nest 1-c (1960) was abandoned at about +11:00 a.m. on May 14, 1960, when part of the thicket on the edge +of which this nest was located was removed by brush-cutters clearing +a power line right-of-way. By 2:00 p.m. this pair had begun +construction of 1-d (1960) in an Osage orange 110 feet southwest of +1-c (1960).</p> + +<p>This particular site is of further interest because it is the same +one utilized for nest 1-a (1960). In all, four instances of utilization +of a nest-site a second time were recorded. Two-a (1960) and +2-d (1960) were built in the same fork; 1-c (1960) and 1-h (1960) +were in the same tree, but not the same fork. It should be mentioned +that 1-a (1960) and 2-a (1960) were abortive attempts that +did not progress beyond the suspension apparatus. Nice (1929:16) +recorded a similar instance of the re-use of a nest tree, but different +forks were used.</p> + +<p>Re-use of an exact nest-site would ordinarily be impossible if +the initial attempt were not abortive, because the presence of a +completed nest would pose problems in construction with which +the birds would probably be unable to cope. (A report by Morse +in Bent, 1950:256 of a double nest indicates that this may not always +be true. At the time of discovery one nest contained two eggs +and the other nest contained young.) Since nests are used only +once there would be no tendency to adopt the old nest. However, +abortive nests, usually little more than a few strands of nesting +material secured to the fork, might stimulate the birds to continue +building. Re-use of a single nest-site in 15.8 per cent of 38 nests +built in 1960 seems to be more than fortuitous circumstance. This +re-use may have physiological benefits in conjunction with apportionment +of energy for other nesting activities, because rapid location +of a nest-site would mean that energy normally expended in +searching and selecting could be rechanneled for actual construction. +In each of the instances of rebuilding, the new nest was +<span class='pagenum'><a name="Page_274" id="Page_274">[Pg 274]</a></span> +begun on the same day that the previous nest was abandoned.</p> + +<p>The re-nesting of pair 9 (1960) is worthy of note. These birds +were established in the elm thicket on Clark land. Elm was by +far the most abundant tree, with dogwood, Osage orange and honey +locust also relatively common. There were only six boxelders in +the territory and yet the four nests built by this pair were placed +in them. This is the only instance of seeming preference.</p> + + +<h4><i>Building</i></h4> + +<p>Nestbuilding by Bell Vireos can be best discussed in terms of +the phases of construction described for the Red-eyed Vireo, Lawrence +(1953:57), which are: (1) construction of the suspension +apparatus, (2) construction of the bag, (3) lining of the bag and +smoothing and polishing of the exterior, and (4) adornment of the +exterior. Red-eyes (Lawrence, 1953:59) may continue adornment +far into the period of incubation. Both the male and female Bell +Vireo have been observed to add spider egg sacs and other silk +to the exterior of the nest as late as the sixth day of incubation.</p> + +<p>Nice (1929:16) recorded only the female Bell Vireo building, +but she did recall, from previous studies, having seen males aiding +somewhat. Pitelka and Koestner (1942:102) wrongly concluded +that the female Bell Vireo builds unaided, but Hensley (1950:243) +observed that both sexes participated in nestbuilding, and Mumford +(1952:229) reported two instances of building by both adults. +His description of the activities viewed in mid-May suggest that +they were of the transitional period between the first and second +phases. On the second occasion he recorded both adults building +during the second phase. Since no details accompany this second +observation I assume that it pertained to activity not necessarily +typical of this phase of construction. Whereas both sexes of the +Bell Vireo cooperate in building the nest, only the female Red-eyed +Vireo builds according to Lawrence (1953:56). But Common +(1934:242) saw both Red-eyed Vireos building a nest.</p> + +<p>The suspension apparatus is constructed by only the male on the +first day. He punctuates each trip to the nest with song. The single +song phrase is given from three to eight times when the male, carrying +nesting material in his bill, arrives in the tree. Typically, he +alights on several perches within the nest tree before flying to the +nest. He often interrupts his work with several songs; when he +has finished adding a load of material he sings from several perches +<span class='pagenum'><a name="Page_275" id="Page_275">[Pg 275]</a></span> +within the nest tree before departing. The male periodically stops +building to court the female.</p> + +<p>In eight hours (494 minutes) of observing the first phase of construction +at five different nests, I saw the female come to the nest +28 times; the male made 95 trips. The female came alone only once, +and brought nesting material ten times, but did not build; on the +other 18 occasions her visits were brief and she usually confined her +activities to an inspection of the nest. Twenty of the visits by the +female were made late in the first phase, marking a gradual transition +to her assumption of building responsibility. (The delay by +the female in beginning to build is puzzling; because all evidence +indicates that she helps select the nest-site, I would expect her to +help with the initial building. There seems to be no clear advantage +in her delay in beginning to build.) The courtship and building +activities of the male plus the presence of a partly completed nest +seem to stimulate the female to commence building. Her visits +become more frequent as construction of the suspension apparatus +nears completion. At a time early in the second day the transition +has taken place, and the female becomes the sole worker.</p> + +<p>On May 7, 1960, male 2 (1960), at the time unmated, was observed +as he came upon a nest of the previous year. The nest, after +a year's weathering, suggested in appearance perhaps an early +second-day nest. The bird flew to the nest and tugged and wove +loose strands of grass for three minutes. Before leaving the site, the +bird sang twice from different perches. This observation suggests +that a partly constructed nest can elicit nestbuilding behavior, even +in an unmated male.</p> + +<p>The techniques of building by the male consist primarily of laying +pieces of grass or bark across the fork, or along one of its branches, +and then fastening them in place with pieces of animal silk. Once +a "racket" has been formed, spider egg cases and plant down are +emplaced among the fibers. The male employs weaving, twisting, +and pecking motions of the head to emplace material.</p> + +<p>As previously indicated, the female is the principal worker in the +second and third phases of construction. The male infrequently +visits the nest, but regularly visits the nest tree. The molding of the +bag is accomplished by piling leaves, grasses and plant down onto +the suspension apparatus. This material is also bound in with animal +silk. As the amount of material accumulates, the female begins to +trample it and gradually the bag takes shape. When trampling is +<span class='pagenum'><a name="Page_276" id="Page_276">[Pg 276]</a></span> +first attempted, the nest often fails to support the female and she +falls through the bottom of the nest. Such an occurrence was observed +on May 23, 1960, on three consecutive trips by female 1 +(1960), in constructing nest 1-e (1960). As the bag deepens, additional +strands of grass are added to the wall and woven into place.</p> + +<p>The male is extremely attentive during this and the following phase. +He follows the female as she gathers nest-material accompanying both +this activity and her building with rapid song; he may give an average +of seven song phrases per minute. The male brings to the nest a strand +of grass, or some other material, about every twentieth trip. He +frequently inspects the nest and the activities of the female from +perches near the nest. Construction of the bag is ordinarily completed +in the third day.</p> + +<p>The third phase, the lining of the interior and the smoothing +of the exterior, involves an additional one and one-half to two days. +Smoothing of the exterior refers to tightening of the grasses woven +into the bag and addition of more animal silk. In lining the nest, +the female stands on one of the branches of the fork and emplaces +one end of a long, thin strand of some relatively stiff piece of +grass or strip of bark. She then jumps into the bag and, while slowly +turning around, pecks it into place, thus coiling the strand neatly +around the interior of the bag.</p> + +<p>As previously mentioned, the fourth phase overlaps the periods +of lining, smoothing, egglaying, and incubation. The principal +activity is the addition of white spider egg sacs to the exterior. +The trips are infrequent; but, occasionally, birds will interrupt +an hour of incubation with three or four minutes of active adornment, +during which several trips may be made. Both sexes participate +in this phase.</p> + + +<h4><i>Gathering of Nesting Material</i></h4> + +<p>Nesting materials were gathered anywhere within the territory. +Occasionally materials were collected from within the nest tree, +but usually they were obtained 20 to 200 feet from the nest-site. +On several occasions I observed birds inspecting stems or branches +where bark was frayed. Loose ends are grasped in the beak and +torn free with an upward jerk of the head. Possibly the notch near +the distal end of the upper mandible aids in grasping these strands. +Plant down is first extracted and then rolled into a ball by means +of the beak while held with the feet before being transported to +the nest.</p> + + +<p><span class='pagenum'><a name="Page_277" id="Page_277">[Pg 277]</a></span></p> +<h4><i>Length and Hours of Nestbuilding</i></h4> + +<p>As indicated by Nolan (1960:230), accurate determination of the length +of nestbuilding is difficult because of continued adornment and +polishing after the nest is functionally complete. Most of the early +nests for which I have records took from four and one-half to five +days to construct. A four-to five-day period of building is reported +by other observers (Nice, 1929:16; Pitelka and Koestner, 1942:99; +Hensley, 1950:242; Nolan, 1960:230).</p> + +<p>One instance of protracted building was recorded. Nest 6-d (1960) was +begun on May 29, 1960, and not completed until nine days later on June +6, 1960. In contrast nest 1-g (1960) begun on May 31, 1960, was +finished three days later on June 2, 1960. Nestbuilding occurs between +the hours of 6:00 a.m. and 5:30 p.m. Heavy rain in the early morning +may delay building.</p> + + +<h4><i>Abortive Nestbuilding Efforts</i></h4> + +<p>Eight of 38 nests started in 1960 were never completed (Table 6). +Six of these abortive attempts were abandoned during, or shortly +after, the completion of the suspension apparatus. Five of these +nests were abandoned because the female did not begin building +following the end of work by the male. The early abandonment of +the other three nests 1-a (1960), 2-c (1960) and 6-e (1960) was +attributable to the interruption of building by the male because of +heavy rain and protracted territorial conflicts. The occurrence of +these abortive nests at any time within the nesting efforts of a single +pair indicates that such attempts are not examples of "false nestbuilding."</p> + + +<h4><i>Renesting</i></h4> + +<p>Renesting after desertion or successful fledging occurs within two +to thirty-six hours. Young were fledged from 1-a (1959) on June +19, 1959, and nest 1-b (1959) was discovered when late in the +second phase of construction on June 22. If the nest was started on +June 20, then renesting took place within 15 hours after fledging.</p> + + +<h4><i>The Nest</i></h4> + +<p>Several authors have described various aspects of the nest of the +Bell Vireo, notably Goss (1891:535); Simmons (<i>in</i> Bent, 1950:256), +Nice (1929:13) and Nolan (1960:230-231). I can add but little to +these descriptions.</p> + +<p>The nest itself is a compact structure composed of strips of bark +and strands of grasses that are interwoven and tightly bound with +<span class='pagenum'><a name="Page_278" id="Page_278">[Pg 278]</a></span> +animal silk. The floor of the cup is first lined with a layer of small +leaves and then the entire interior is lined with fine stems or strips +of bark. Feathers are occasionally used to pad the bottom prior to +lining, as are pieces of wool and milkweed down. Nest 2-e (1960) +had been packed with small pieces of soil bearing moss prior to +lining.</p> + +<h4><span class="smcap">Table 6. Abortive Nesting Attempts in May and June of 1960.</span></h4> + +<table border="1" cellpadding="2" cellspacing="0" summary="Abortive Nesting Attempts"> +<tr> + <th>Nest</th> + <th>Length of time worked on</th> + <th>Cause of abandonment</th> +</tr> +<tr> + <td>1-a</td> + <td>1 day</td> + <td>Heavy rain</td> +</tr> +<tr> + <td>1-h</td> + <td>2 days</td> + <td>Female failed to build</td> +</tr> +<tr> + <td>2-a</td> + <td>1/2 day</td> + <td>Female failed to build</td> +</tr> +<tr> + <td>2-c</td> + <td>1 day</td> + <td>Protracted territorial dispute</td> +</tr> +<tr> + <td>4-a</td> + <td>1 day</td> + <td>Female failed to build</td> +</tr> +<tr> + <td>5-a</td> + <td>1 day</td> + <td>Female failed to build</td> +</tr> +<tr> + <td>6-c</td> + <td>1 day</td> + <td>Heavy rain</td> +</tr> +<tr> + <td>7-a</td> + <td>2 days</td> + <td>Female failed to build</td> +</tr> +</table> + +<p>Early nests tend to be bulkier, having thicker walls and bottoms +than later efforts. However, nests in May were found to have 16 +per cent thicker bottoms and 41 per cent thicker walls than nests +in June (Table 7). Standard nest measurements do not show this +to be so, for the exterior and interior diameters at the rim are governed +by the angle between the two branches of the fork.</p> + +<h4><span class="smcap">Table 7. Dimensions of Nests in May (1960) and June (1960).</span></h4> + +<table border="1" cellpadding="2" cellspacing="0" summary="Dimensions of Nests"> +<tr> + <th>Measurements</th> + <th>May (N 10)</th> + <th>June (N 8)</th> +</tr> +<tr> + <td>External depth</td> + <td>61.6 mm.</td> + <td>59.3 mm.</td> +</tr> +<tr> + <td>Depth of cup</td> + <td>45.5 mm.</td> + <td>46.3 mm.</td> +</tr> +<tr> + <td>Outside diameter</td> + <td>57.3/55.5 mm.</td> + <td>54.3/53.5 mm.</td> +</tr> +<tr> + <td>Inside diameter</td> + <td>43.4/42.2 mm.</td> + <td>45.5/43.9 mm.</td> +</tr> +<tr> + <td>Thickness of forward wall 1 inch below rim</td> + <td>13.8 mm.</td> + <td>7.6 mm.</td> +</tr> +<tr> + <td>Thickness of bottom</td> + <td>11.3 mm.</td> + <td>4.6 mm.</td> +</tr> +</table> + + + +<hr style="width: 65%;" /> +<h2><a name="EGGLAYING_AND_INCUBATION" id="EGGLAYING_AND_INCUBATION"></a>EGGLAYING AND INCUBATION</h2> + + +<h4><i>Egglaying</i></h4> + +<p>Egglaying begins the first or second day after completion of the nest. +The female sits in the nest occasionally for periods of five to +twenty-five minutes on the day the nest is completed. This is +interrupted by periods of nest-adornment and foraging; such activities +sometimes keep the female off the nest for several hours. Prior to the +laying of the first egg, only the female is seen on the +<span class='pagenum'><a name="Page_279" id="Page_279">[Pg 279]</a></span> +nest, although the male is often seen sitting quietly within the nest tree a +few feet from the female. The infrequency of the "congested" song and +the alarm (<i>eh-eH-EH</i>) after the inception of "broodiness" indicates +the waning of courtship behavior. As later in incubation only the +"normal" song and the scold are heard.</p> + +<p>Eggs are laid early in the morning prior to 5:30 a. m. according to +Nolan (1960:232). The nest is usually left unoccupied for considerable +periods after the first egg is laid, but, on the first day of laying, +both sexes have been observed sitting for brief periods averaging ten +minutes in length. Eggs are laid at one-day intervals until completion +of the clutch. I found incubation to begin with the second egg.</p> + + +<h4><i>Clutch-size</i></h4> + +<p>The average clutch-size of the Bell Vireo in Kansas, based on +thirty-three records, is 3.39 eggs (Table 8). Seasonally, the largest +average clutches are produced in the middle of the breeding season, +that is, in June. Lack (1947:308-309) indicates that in European +passerines the highest seasonal average clutch-sizes likewise occur +in June. The largest average clutch-size in the Bell Vireo is presumably +related to some aspect of the availability of food.</p> + +<h4><span class="smcap">Table 8. Average Numbers of Eggs per Nest (Number of Records in +Parentheses)<a name="FNanchor_A_6" id="FNanchor_A_6"></a><a href="#Footnote_A_6" class="fnanchor">[F]</a>.</span></h4> + +<table border="1" cellpadding="2" cellspacing="0" summary="Average Numbers of Eggs per Nest"> +<tr> + <th>Year</th> + <th>May</th> + <th>June</th> + <th>July</th> + <th>Mean annual clutch-size</th> +</tr> +<tr> + <td>1959<br />1960</td> + <td>3.0 (7)<br />3.3 (6)</td> + <td>3.2 (12)<br />3.83 (5)</td> + <td>3.0 (1)<br />4.0 (2)</td> + <td align="center">3.06<br />3.72</td> +</tr> +<tr> + <td>1959-1960</td> + <td>3.17</td> + <td>3.52</td> + <td>3.5</td> + <td align="center">3.39</td> +</tr> +</table> + +<div class="footnote"><p><a name="Footnote_A_6" id="Footnote_A_6"></a><a href="#FNanchor_A_6"><span class="label">[F]</span></a> +These data have been supplemented from the literature pertinent to Kansas.</p></div> + +<p>Caution is necessary in determining mean clutch-size in the Bell +Vireo. Eggs occasionally disappear from the nest prior to or during +incubation, without subsequent addition of cowbird eggs. Unfamiliarity +with the history of such a nest on the part of the observer +would lead to an inaccurate determination of clutch-size.</p> + +<p>Complete clutches are not replaced with the same regularity as +are nests. I have recorded intervals of six to thirty days between +successive clutches. Successful replacement of clutches is determined +by a number of factors: nest-site, completion of a nest, +weather, predation, and parasitism by the cowbird. The difference +<span class='pagenum'><a name="Page_280" id="Page_280">[Pg 280]</a></span> +between the number of renesting attempts and the successful replacement +of clutches seems to indicate that different physiological +processes are responsible for these two phenomena and that there +is lack of synchrony between them. The development of the ovarian +follicle requires a specific number of days that is not always coincident +with the building of replacement nests. If, in the Bell Vireo, +replacing a nest were solely a responsibility of the female, instead +of involving the male to a considerable extent, it would seem likely +that replacement of nests and the replacement of clutches would +be more closely coordinated.</p> + + +<h4><i>Incubation</i></h4> + +<p>Nice (1954:173) considers the incubation period to be the elapsed time +between the laying of the last egg in a clutch and the hatching of +that egg, when all eggs hatch. My data indicate that, normally, +intensive incubation begins when the second egg is laid and lasts +fourteen days in the Bell Vireo. Nice (1929:99) also considered the +incubation period in this species to be fourteen days but believed it +to commence when the third egg was laid. Pitelka and Koestner +(1942:99) noted that the first and second eggs hatched fourteen days +after laying of the second egg. However, they thought incubation began +with the first egg. This would mean a fifteen-day period for this egg. +All the eggs that Nolan (1960:234) marked hatched in approximately +fourteen days. Eight eggs artificially incubated by Graber (1955:103) +required an average of 15.01 days to hatch. As Van Tyne and Berger +(1959:293) indicate, periods of sitting on the nest, even all night, +do not necessarily mean that incubation has begun, for it has been +demonstrated in several species that birds may sit on an egg without +actually applying heat. My own observations demonstrate that the first +egg may be left unattended for several hours at a time on the day that +it is laid.</p> + + +<h4><i>The Roles of the Sexes in Incubation</i></h4> + +<p>Both the male and female sit on the eggs in the daytime. My study of +histological sections of ventral epidermis indicates that the male +does not possess a brood patch; the increased vascularization typical +of the brood patch in females is not evident in males. But, the male +loses most of the down feathers of the ventral apterium. Also, +according to Bailey (1952:128), the male Warbling Vireo that sits on +the eggs lacks a brood patch.</p> + +<p>Bailey (1952:128) suggests that male passerines lacking brood +patches that habitually sit on eggs do not heat the eggs. Thus it +<span class='pagenum'><a name="Page_281" id="Page_281">[Pg 281]</a></span> +cannot be considered true incubation since no increase of temperature in the +eggs is effected by such means. He further notes that it is at night +when eggs are likely to experience a drop in temperature that +embryonic development will be impaired. I have no data directly +pertaining to which sex sits at night, but it is presumably the +female, because she is always seen on the nest early in the morning +and late in the evening.</p> + +<div class="figcenter" style="width: 70%;"> +<img src="images/i043.jpg" width="100%" alt="Fig. 4." title="Fig. 4." /> +<span class="caption"><span class="smcap">Fig. 4.</span> Comparison of periods of incubation by both +sexes in cold (54° F.) rainy weather (A) and in warm (82° F.) sunny weather (B).</span> +</div> + +<p>If a highly-vascularized brood patch is essential for true incubation, +then it is surprising that males take regular turns on the nest in +cold, rainy weather. On May 20, 1960, male 3 (1960) sat on the +eggs longer than did the female (fig. 4). The temperature during +<span class='pagenum'><a name="Page_282" id="Page_282">[Pg 282]</a></span> +this hour and a half of incubation was 54° F. One solution to this +problem is supplied by Skutch (1957:74). He indicates that, "the +type of the incubation is determined largely by innate factors, so +that it persists through fairly wide fluctuations in weather, although +it may break down in extreme conditions." Obviously then, in the +example described above, the weather conditions do not qualify as +"extreme." Sitting by the male is certainly functional to some extent +for it relieves the female to forage; furthermore, the eggs are sheltered +from inclement weather and protected from predators. Nolan +(1960:232) suggests similar reasons for incubating by the male +and adds the "conservation of heat supplied to the eggs by the female."</p> + +<div class="figcenter" style="width: 65%;"> +<img src="images/i044.jpg" width="100%" alt="Fig. 5." title="Fig. 5." /> +<span class="caption"><span class="smcap">Fig. 5.</span> Daily participation in incubation +as indicated by the sex of the adult on the nest upon approach of the observer.</span> +</div> + +<p>My data, based on incubation beginning with the second egg, indicate +that the female incubates more often daily than the male (fig. 5). The +male sits on the eggs only occasionally in the morning, but almost as +often as the female in the afternoon. Nolan (1960:233) found that 95.5 +per cent of the male's time on the nest and only 40 per cent of the +female's time were attributable to the early hours of the day. +Although I lack data on the critical hours of 5:00 a.m. to 6:59 a.m., +I have enough observations (20) from 7:00 a.m. to 9:00 a.m. to +indicate that the males sit on the eggs infrequently (3 of 20 +instances) in those hours. The discrepancy in the two sets of data, +which may be merely an artifact of sampling techniques, does suggest +two possible alternatives: (1) the male +<span class='pagenum'><a name="Page_283" id="Page_283">[Pg 283]</a></span> +sits on the eggs in the morning and gives the female, who sits on the +eggs throughout the night, an extended rest and an opportunity to +forage; (2) the female continues to sit throughout the morning, +especially during the early hours of daylight, a time of day when the +temperature may still be low enough to impair development of the +embryo.</p> + + +<h4><i>Relief of Partners in Incubation</i></h4> + +<p>Relief of partners involves some ceremony. When the female is +incubating, the male sings several times as he approaches the nest +tree; the female responds with several <i>chees</i>, but otherwise remains +immobile. The male sings several more times upon alighting in the +nest tree whereupon the female <i>chees</i> again and flies directly from +the nest. A few seconds later the male appears at the edge of the +nest and, after inspecting the eggs, hops in and settles upon them. +When the male is sitting he is notably anxious prior to an exchange +with the female, often arising and craning his neck as he surveys the +surrounding vegetation, seemingly searching for his mate. The +singing of the male and the calling of the female serve as signals, +coordinating the exchange.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="NESTLING_PERIOD" id="NESTLING_PERIOD"></a>NESTLING PERIOD</h2> + + +<h4><i>Hatching Sequence</i></h4> + +<p>As indicated earlier, hatching normally occurs fourteen days after +the second egg is laid. Hatching of the young was staggered at +three nests under observation. In nest 2-b (1959) the first young +hatched on June 8, 1959, the second on June 10. In 3-b (1959) +one young hatched each day from the 12th through the 14th of +June. In 5-a (1959) two young hatched on June 15, the third on +June 16, and the fourth on June 17. Size of the young differed +notably for about three days as a result of staggered hatching, but +after that day the younger birds tended to catch up in size with +their older brood-mates. The fourth young in nest 5-a (1959) +grew steadily weaker and was missing from the nest on June 23, +1959. Staggered hatching is usually thought to be related to the +availability of food that will insure survival of at least some of the +nestlings when a shortage of food exists. It is doubtful that staggered +hatching has adaptive significance in the Bell Vireo, since +there seems to be no shortage of food for the young. In small +passerines such as the Bell Vireo the principal problem is to insure +fledging as quickly as possible because of the danger from predators.</p> + + +<p><span class='pagenum'><a name="Page_284" id="Page_284">[Pg 284]</a></span></p> +<h4><i>Development of the Nestlings</i></h4> + +<p>Young are pinkish at hatching and devoid of visible natal down. +Du Bois (<i>in</i> Wetherbee, 1957:380), inspected day-old nestlings by +means of a magnifying glass and was unable to detect any down. +Nolan (1960:236) also indicates that the young are naked at birth +and that the "body color is between flesh and rufous except +where folds of the straw yellow skin obscure the underlying colors." +The Hutton Vireo (<i>Vireo huttoni</i>) is essentially naked at birth, +save for sparse hairlike down on the head and back (Wetherbee, +1953:380). The Red-eyed Vireo, according to Lawrence (1953:67) +is naked at birth save for a sparse covering of greyish natal +down, on the head, shoulders, and back.</p> + +<p>In the Bell Vireo the pterylae darken slightly on the second day +and the color becomes more intense daily until the quills of the +dorsal tracts, the wings, and the tail break from their sheaths on +the sixth day. In Red-eyed Vireos the pterylae darken by the end +of the first day and the quills break through the skin on the fifth +day, erupting from the sheaths by the seventh day (Lawrence, +1953:67).</p> + +<p>From the first day the young are able to squeak. Poking a young +bird was sufficient to elicit this sound, phonetically a nasal <i>peek</i>. +The only other vocalization noted throughout the nestling period +was an abbreviated <i>chee</i>.</p> + +<p>For the first three days tapping the nest or even movement of it +caused by wind would elicit begging. By the fifth day at nest 2-a +(1959) only vigorous agitation of the branch to which the nest was +<span class='pagenum'><a name="Page_285" id="Page_285">[Pg 285]</a></span> +attached evoked any response. At this nest on June 16, 1959, one +young begged while the other cowered. Cowering is correlated +with opening of the eyes, as the young bird that begged had its +eyes only partly open. Both young cowered on June 19, 1959. +Table 9 summarizes the maturation of the nestling Bell Vireos.</p> + +<h4><span class="smcap">Table 9. Maturation of Nestling Bell Vireos. The First Day That an +Activity Was Observed Is Shown.</span></h4> + +<table border="1" cellpadding="2" cellspacing="0" summary="Maturation of Nestling Bell Vireos"> +<tr> + <th> </th> + <th colspan="11">Day of nestling life</th> +</tr> +<tr> + <th> </th> + <th>1</th> + <th>2</th> + <th>3</th> + <th>4</th> + <th>5</th> + <th>6</th> + <th>7</th> + <th>8</th> + <th>9</th> + <th>10</th> + <th>11</th> +</tr> +<tr> + <td>Eyes open</td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td>x</td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> +</tr> +<tr> + <td>Feathers erupt</td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td>x</td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> +</tr> +<tr> + <td>Sound: Squeak</td> + <td>x</td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> +</tr> +<tr> + <td>Sound: <i>Chee</i></td> + <td> </td> + <td> </td> + <td> </td> + <td>x</td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> +</tr> +<tr> + <td>Begging</td> + <td>x</td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> +</tr> +<tr> + <td>Cowering</td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td>x</td> + <td> </td> + <td> </td> + <td> </td> +</tr> +<tr> + <td>Head scratching and Preening</td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td>x</td> + <td> </td> + <td> </td> +</tr> +<tr> + <td>Hopping to rim of nest</td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td>x</td> + <td> </td> + <td> </td> +</tr> +<tr> + <td>Fledging</td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td> </td> + <td>x<a name="FNanchor_A_7" id="FNanchor_A_7"></a><a href="#Footnote_A_7" class="fnanchor">[G]</a></td> +</tr> +</table> + +<div class="footnote"><p><a name="Footnote_A_7" id="Footnote_A_7"></a><a href="#FNanchor_A_7"><span class="label">[G]</span></a> +This is the commonest fledging day.</p></div> + + +<h4><i>Parental Behavior</i></h4> + +<p>No eggshells were found in nests on the days of hatching. Presumably +they had been removed by the parents. Nolan (1960:234) indicates +immediate disposition of the eggshell after hatching. Lawrence +(1953:62) suggests that conspicuous removal of eggshells by the female +Red-eyed Vireo informs the male that the young have hatched.</p> + +<p>Both sexes brood and the exchange of partners resembles that +described for the incubation period. Decrease in brooding in the +daytime begins about the sixth day of nestling life. Nolan (1960:235) +reports a sharp decrease in brooding when the oldest nestlings +are seven days old. Brooding decreases notably on the sixth day +of nestling life in the Red-eyed Vireo (Lawrence, 1953:62). Nice +(1929:17), Hensley (1950:244), and Nolan (1960:235) report that +the female Bell Vireo assumes a slightly greater role in brooding +than the male.</p> + +<p>Apparent sun-shading was noted at nest 3-b (1959) at 2:00 p.m. on June +17, 1959, on the fifth day of the nestling period. The nest contained +three young. An adult flew to the nest; while standing on its rim the +bird dipped its head into the nest six times, afterward appeared to be +eating a fecal sac, than shifted position to the unattached portion of +the rim, gaped three times, thereupon spread its wings, and sat +motionless 35 minutes. In this attitude it formed an effective shield +sheltering the young from direct sunlight penetrating the thin foliage +of the honey locust in which the nest was situated. The temperature at +this time was 95° F., but the sky was partly cloudy. By 2:30 p.m. the +sky had become overcast and the sun passed behind a cloud. Although +sunlight no longer fell directly upon the nest, the bird remained in +the shielding posture for another five minutes before flying from its +perch. Sun-shading was not observed at either of the other nests +containing young; dense overhead vegetation protected those nests. +Sun-shading has been noted in other species where the nest was poorly +protected from the sun. Lawrence (1953:62) observed this behavior at +two Red-eyed Vireo nests in conifers. The "sun-shield" posture of the +Bell Vireo does not correspond to any of the sunning postures +described by Hauser (1957).</p> + + +<p><span class='pagenum'><a name="Page_286" id="Page_286">[Pg 286]</a></span></p> +<h4><i>Feeding of the Nestlings</i></h4> + +<p>Both sexes fed the young, and presumably began shortly after the +first nestling hatched. My data indicate that the female does more +feeding than the male (Table 10); in about eight hours of observation +a total of 67 morsels were brought, 43 by the female and 24 by +the male, for an average of once every 7.6 minutes. Nice (1929:17), +however, observed a male to bring food 53 times as compared to +21 visits by the female. In five and one-half hours of watching, +meals were brought once every 4.9 minutes. Du Bois (<i>in</i> Bent, +1950:257) recorded seven trips in an hour and forty minutes, or one +every fourteen minutes.</p> + +<p>At three nests containing young the adults were sometimes silent +and sometimes vocal on their approach. The female often emitted +a subdued <i>chee</i> which, coupled with the vibration of the nest caused +by her arrival, elicited begging behavior from the young. None of +the males was heard to utter such a call, but I have the impression +that they often did call although I failed to hear the sounds. The +males did, on occasion, sing several songs as they approached, even +with food held in their beaks. Such singing elicited begging from +the nestlings. Once the eyes of the young were open they often +began begging when a silent adult was within two or three feet of +the nest; begging behavior probably is elicited by tactile, auditory +or visual stimuli in that order, or, as the nestling period proceeds, +by any combination of these stimuli.</p> + +<h4><span class="smcap">Table 10. Feeding of the Nestlings.</span></h4> + +<table border="1" cellpadding="2" cellspacing="0" summary="Feeding of the Nestlings"> +<tr> + <th rowspan="2">Day of nestling period</th> + <th rowspan="2">Length of observation</th> + <th colspan="2">Adult involved</th> +</tr> +<tr> + <th>Male</th> + <th>Female</th> +</tr> +<tr> + <td>1</td> + <td>30 min.</td> + <td>3</td> + <td>5</td> +</tr> +<tr> + <td>2</td> + <td>60 min.</td> + <td>1</td> + <td>4</td> +</tr> +<tr> + <td>3</td> + <td>60 min.</td> + <td>2</td> + <td>5</td> +</tr> +<tr> + <td>4</td> + <td>30 min.</td> + <td>1</td> + <td>4</td> +</tr> +<tr> + <td>7</td> + <td>60 min.</td> + <td>4</td> + <td>7</td> +</tr> +<tr> + <td>2</td> + <td>60 min.</td> + <td>3</td> + <td>3</td> +</tr> +<tr> + <td>6</td> + <td>60 min.</td> + <td>3</td> + <td>6</td> +</tr> +<tr> + <td>7</td> + <td>30 min.</td> + <td>3</td> + <td>3</td> +</tr> +<tr> + <td>9</td> + <td>60 min.</td> + <td>4</td> + <td>6</td> +</tr> +<tr> + <td><b>Totals</b></td> + <td><b>510 min.</b></td> + <td><b>24</b></td> + <td><b>43</b></td> +</tr> +</table> + +<p>Not all trips made by parents resulted in successful feeding of +young; some visits seemed to be purely for inspecting the young. +<span class='pagenum'><a name="Page_287" id="Page_287">[Pg 287]</a></span> +On other occasions the adults experienced difficulty in transferring +food to the young, and, thus thwarted, would themselves eat the +food. Nice (1929:17) estimated that from five to twelve of a total +of seventy-five meals were eaten by adults.</p> + + +<h4><i>Nest Sanitation</i></h4> + +<p>Both parents regularly removed fecal sacs from the nest, eating +them for the first five days and thereafter carrying them off and +presumably dropping them. It is doubtful that fecal sacs were +actively removed in the last two days of nestling life as the bottoms +of nests from which young flew away were invariably covered with +excrement.</p> + +<p>On several occasions a parent brought food to the nest and then +remained perched on the rim alternately peering into the nest and +then preening. Once bill swiping was observed and another time +an adult male sang once. The adult remained at the nest from +twenty seconds to a full minute.</p> + + +<h4><i>Fledging</i></h4> + +<p>Eight young were fledged from the four nests in 1959. The +nestling period lasted from nine to twelve days. Human interference +may have been largely responsible for the fledging of the +young at nine days. Pitelka and Koestner (1942:100) found nestling +life to last eleven days. Nolan (1960:235) reports nestling periods +varying from 10.5 to 12 days. The young Red-eyed Vireo is ready +to leave the nest at ten days but often remains an additional day +before departing (Lawrence, 1953:68).</p> + +<p>The oldest nestling at nest 2-a (1959) hopped out on June 17, +1959, when I disturbed the parents. On this date the juvenal +plumage was only partly developed and the young bird was incapable +of flight. By the tenth day of nestling life the young in all +the nests were observed to hop to the rim, flutter their wings, hop +back into the nest and also to preen and scratch their heads. The +young at fledging are usually completely feathered, but have notably +short tails and relatively short, stubby wings. According to Ridgeway +(1904:205) the juvenal plumage is much like that of the adult.</p> + + +<h4><i>Nest Parasites</i></h4> + +<p>Pitelka and Koestner (1942:103) found that incubating adults and later +the young suffered infestation of the northern fowl mite, +<i>Ornithonyseus sylviarum</i>. Nolan (1960:241) reports a heavy +infestation of this mite at four nests. Unidentified mites were noted +at four nests in my study area in 1959. Incubating adults were +<span class='pagenum'><a name="Page_288" id="Page_288">[Pg 288]</a></span> +observed to peck at their breasts and scapulars from the eleventh +through the fourteenth day of incubation. Serious infestations were +not noted at the nests until the ninth day of nestling life. At this +time the young were observed to scratch their heads and peck at their +breasts, scapulars, and the base of their tails. On the day of +fledging the nests were a seething mass of crawling mites; the mites +also extended well up the branches to which the nests were attached. +Nest 1-a (1959), which was discovered on June 18, 1959, presumably on +the day after fledging, was densely covered with mites. Some mites +were still crawling on this nest on June 20, 1959.</p> + + + +<hr style="width: 65%;" /> +<h2><a name="FLEDGLING_LIFE" id="FLEDGLING_LIFE"></a>FLEDGLING LIFE</h2> + + +<p>On June 20, 1959 I located one young 80 feet northeast of nest 2-a +(1959), about five hours after it had left the nest. One parent was +observed to feed it once. No young were seen thereafter from this or +any other nest. Extreme agitation on the part of one or both parents +on several occasions shortly thereafter, however, suggested the +proximity of the young. Search in the immediate vicinity on each of +these occasions proved fruitless. Three days after fledging their +young, pair 2 (1959) was primarily occupied with courtship activities. +Pair 1 (1959) was involved in courtship and nestbuilding one and +one-half days after the apparent fledging of their young. Nolan +(1960:238) indicates that the young remain within the territory and +perhaps are fed by the parents up until an age of about 40 days. +Sutton (1949:25) and Lawrence (1953:68) present contradictory reports +on fledgling-parent relationships in the Red-eyed Vireo. Sutton +concluded that the young quickly took leave of their parents whereas +Lawrence reported a young bird being fed 35 days after fledging.</p> + + +<h4><i>Second Broods</i></h4> + +<p>The curve based on 66 nesting records of the Bell Vireo representing +the breeding activity in northeastern Kansas demonstrates +a tendency toward double-broodedness (fig. 6). The peak of the +breeding season is from May 20 to June 20. The large number +(20) of replacement nests built in late May of 1960 tends to distort +the curve of the breeding data; a second peak about 35 days after +the first is evident.</p> + +<p>I am of the opinion that the vast majority of vireos are single-brooded +solely by virtue of the limited success of early nesting +efforts, and that in "good" years most pairs would be double-brooded. +<span class='pagenum'><a name="Page_289" id="Page_289">[Pg 289]</a></span> +Each of the four pairs that successfully raised one brood +in my study area in 1959 renested within a day or two after the +fledging of the young. I do not know the fate of these nests. Nolan +(1960:237) reports at least one instance of a second brood in the +course of his study. Nolan (<i>op. cit.</i>) notes that the literature, in +general, indicates that vireos are double-brooded, but that his +evidence, mentioned previously, is the only evidence based on +banded birds.</p> + +<div class="figcenter" style="width: 80%;"> +<img src="images/i051.jpg" width="100%" alt="Fig. 6." title="Fig. 6." /> +<span class="caption"><span class="smcap">Fig. 6.</span> Breeding season in northeastern Kansas based on +the number of completed clutches in each 10-day period from May through July.</span> +</div> + + + +<hr style="width: 65%;" /> +<h2><a name="REPRODUCTIVE_SUCCESS" id="REPRODUCTIVE_SUCCESS"></a>REPRODUCTIVE SUCCESS</h2> + + +<p>Only four nests were successful; all of these were observed in +1959. The principal external factors responsible for nesting failure +were severe weather, predation, parasitism by Brown-headed Cowbirds +(<i>Molothrus ater</i>) and human interference (Table 11).</p> + +<p>In late winter and early spring of 1960 heavy snow, continuously +at a depth of at least 10 inches, covered most of the Mid-west from +February 20 through March 20. Consequently, the growing season +was some two weeks behind that of 1959. Of all the species in the +<span class='pagenum'><a name="Page_290" id="Page_290">[Pg 290]</a></span> +study area, the Bell Vireo is the most dependent on dense foliage +for cover and concealment for its nests. Consequently the tardiness +of the season seemingly negatively influenced reproductive success +of this more than any other species of bird in the study area.</p> + + +<h4><i>Behavior</i></h4> + +<p>Several aspects of the behavior of the Bell Vireo tend to contribute +to nesting failure. They include:</p> + +<p>1. Nest-site. Nests are occasionally suspended from exposed +branches. Occurrences of this sort suggest that the dimensions of +the fork are more important in the choice of a site than availability +of cover.</p> + +<p>2. Song. The loud, continuous song of the male during nestbuilding +alerts cowbirds and predators to the presence of a nest. +The incongruous habits of the male of singing in the nest tree and +while sitting on the nest may facilitate location by some enemies, +particularly cowbirds.</p> + +<h4><span class="smcap">Table 11. Egg Mortality in Bell Vireos.</span></h4> + +<table border="1" cellpadding="2" cellspacing="0" summary="Egg Mortality"> +<tr> + <th>Mortality agents</th> + <th>N<a name="FNanchor_A_8" id="FNanchor_A_8"></a><a href="#Footnote_A_8" class="fnanchor">[H]</a></th> + <th>Eggs (N-29)<br />1959 Per cent</th> + <th>N</th> + <th>1960 Per cent</th> +</tr> +<tr> + <td>Predation</td> + <td>4</td> + <td>13.8</td> + <td>5</td> + <td>10</td> +</tr> +<tr> + <td>Weather</td> + <td>2</td> + <td>6.9</td> + <td>8</td> + <td>16</td> +</tr> +<tr> + <td>Cowbird</td> + <td>14</td> + <td>48.3</td> + <td>37</td> + <td>74</td> +</tr> +<tr> + <td><b>Totals</b></td> + <td><b>20</b></td> + <td><b>69<a name="FNanchor_B_9" id="FNanchor_B_9"></a><a href="#Footnote_B_9" class="fnanchor">[I]</a></b></td> + <td><b>50</b></td> + <td><b>100</b></td> +</tr> +</table> + +<div class="footnote"><p><a name="Footnote_A_8" id="Footnote_A_8"></a><a href="#FNanchor_A_8"><span class="label">[H]</span></a> +Number of eggs out of the total number laid lost to mortality agents.</p></div> + +<div class="footnote"><p><a name="Footnote_B_9" id="Footnote_B_9"></a><a href="#FNanchor_B_9"><span class="label">[I]</span></a> +In 1959 nine eggs were successful (ultimately gave rise to fledglings).</p></div> + +<p>I am not fully convinced that song from the nest is simply a +"foolish" habit, since snakes, the principal predators with which +this species has to contend, are deaf. My own field observations +and the circumstances of the innumerable instances recorded in the +literature of male vireos singing from the nest suggest that this is a +function of the proximity of the observer. As mentioned elsewhere, +vocal threat is the initial as well as the primary means by which +territory is maintained. Song from the nest evoked by an enemy +also serves to alert the female to danger.</p> + +<p>3. Flushing. The Bell Vireo normally relies upon cryptic behavior +to avoid detection at the nest. Most sitting birds, especially +the females, either flush silently when an enemy is about forty feet +<span class='pagenum'><a name="Page_291" id="Page_291">[Pg 291]</a></span> +from the nest or remain sitting upon the nest tenaciously, refusing +to flush even when touched or picked up. Some birds flushed at +intermediate distances of from three to fifteen feet. In so doing +they revealed the location of their nests. Since none of these +"intermediate flushers" enjoyed nesting success there is possibly +some correlation between these two factors.</p> + + +<h4><i>Predation</i></h4> + +<p>Several complete clutches being incubated disappeared from +nests that were unharmed. Absence of eggshells in the vicinity suggests +predation by snakes.</p> + +<p>On May 25, 1960, I found a <i>Peromyscus</i> climbing toward nest 1-a +(1960). The mouse moved to within two inches of the nest whereupon +I removed the mouse. Such small rodents constitute another +potential source of predation.</p> + + +<h4><i>Cowbird Parasitism</i></h4> + +<p>In this study the failure of 12 of 35 nests can be directly attributed +to cowbird interference. It is well established that the incidence +of cowbird parasitism of Bell Vireo nests is high (Friedmann, +1929:237; Bent, 1950:260-261). Nolan (1960:240) found only one +nest of eight studied to be parasitized by cowbirds. He indicates +that this is surprising in view of the heavy molestation of the Prairie +Warbler (<i>Dendroica discolor</i>) in the same region. A possible +explanation of this phenomenon seems to lie in the much greater +abundance of the Prairie Warbler in comparison to that of the +Bell Vireo. In my study area the incidence of cowbird parasitism +on Bell Vireos in 1959 and 1960 greatly exceeded that of all other +nesting species that were parasitized (Table 12).</p> + +<p>As indicated previously, the female Bell Vireo leaves the nest +unoccupied several hours at a time in the transition period between +completion of the nest and the start of egglaying. Such behavior +early in the morning certainly would facilitate deposition of cowbird +eggs. Early in the nesting period the mere presence of a +cowbird egg in the nest prior to the laying of the host's first egg +leads to abandonment of the nest. This seems to be correlated +with the relative strength of the nesting tendency; anyhow cowbird +eggs laid in later nests prior to the appearance of the host's own +eggs did not cause the nesting birds to desert. The Bell Vireo does +abandon the nest when all but one of its own eggs have been removed +by the cowbird. Mumford (1952:232) records the removal of a cowbird +egg by the host birds and I recorded a similar instance +<span class='pagenum'><a name="Page_292" id="Page_292">[Pg 292]</a></span> +involving nest 2-b (1960). On May 14, 1960, I found one punctured cowbird egg on +the ground about 10 feet west of this nest. Occasionally a cowbird egg +is buried beneath the lining of a nest. Mumford (1952:23) observed +this in mid-May in 1951 and I observed pair 8 (1960) actively covering +with building material a cowbird egg on July 5, 1960. Covering a +cowbird egg constitutes effective removal. Since the egg cannot be +turned, an adhesion develops.</p> + +<h4><span class="smcap">Table 12. Incidence of Cowbird Parasitism of the Bell Vireo Compared +With Other Passerines in the Study Area in 1959 and 1960.</span></h4> + +<table border="1" cellpadding="2" cellspacing="0" summary="Cowbird Parasitism"> +<tr> + <th> </th> + <th>Bell Vireo</th> + <th>Other passerines</th> +</tr> +<tr> + <td>Total nests examined containing at least one host egg</td> + <td>35</td> + <td>43</td> +</tr> +<tr> + <td>Total nests parasitized</td> + <td>24</td> + <td>14</td> +</tr> +<tr> + <td>Total number of cowbird eggs</td> + <td>33</td> + <td>23</td> +</tr> +<tr> + <td>Per cent of nests parasitized</td> + <td>68.6</td> + <td>32.6</td> +</tr> +<tr> + <td>Total number of cowbird eggs per nest</td> + <td>.94</td> + <td>.54</td> +</tr> +</table> + +<p>The percentage of cowbird eggs hatched in relation to the number laid +is relatively low. For instance, Mumford (1952:231) has only one +record of a young cowbird successfully raised by a Bell Vireo. The +data available in Bent (1950:260-261) also indicate that the +percentage of cowbird eggs hatched is small. The Bell Vireo is less +tolerant of cowbird parasitism than are many of the species so +victimized, but is not so intolerant as the Robin, Catbird, and the +Yellow-breasted Chat (Friedmann, 1929:193).</p> + + + +<hr style="width: 65%;" /> +<h2><a name="SUMMARY" id="SUMMARY"></a>SUMMARY</h2> + + +<p>1. The behavior of a small population of Bell Vireos was studied +in the spring and summer of 1959 and again in 1960 in Douglas +County, Kansas, and results are compared with previous studies +elsewhere.</p> + +<p>2. The Bell Vireo sings more often daily and throughout the +nesting season than do the majority of its avian nesting associates. +Six types of vocalizations are readily distinguishable in the field: +primary song, courtship song, distress call, alarm note, specialized +male call note or <i>zip</i>, and the generalized call note or <i>chee</i>.</p> + +<p>3. Territories are established in early May and occupied throughout +the breeding season and post-breeding season. The average +<span class='pagenum'><a name="Page_293" id="Page_293">[Pg 293]</a></span> +size of the territories in 1960 was 1.25 acres. Shifting of territorial +boundaries occasionally occurs after nesting attempts.</p> + +<p>4. Territory is maintained primarily by song, but at least five +aggressive displays are manifest in the early phases of territorial +establishment. These include: (a) vocal threat, (b) head-forward +threat, (c) wing-flicking and sub-maximal tail-fanning, (d) ruffling +and maximum tail-fanning, and (e) supplanting attack.</p> + +<p>5. The precise mechanism of pair-formation in the Bell Vireo +is not known. Early courtship activities are characteristically violent +affairs. Absence of sexual dimorphism suggests that behavioral +criteria are used by the birds in sex-recognition; the male is dominant +and the female is subordinate.</p> + +<p>6. The principal displays associated with courtship include: +greeting ceremonies, "pouncing," "leap-flutter," pre- and post-copulatory +displays, and the posture, copulation. The marked similarity +between elements of courtship display and aggressive display suggests +common origin or the derivation of one from the other.</p> + +<p>7. The nest-site probably is selected by the female. Nests are +suspended from lateral or terminal forks about 2 feet 3 inches high +in small trees and shrubs averaging 11 feet 2 inches in height.</p> + +<p>8. Nestbuilding is intimately associated with courtship and is a +responsibility of both sexes. The male builds the suspension apparatus +and the female constructs and lines the bag. Both sexes +participate in adorning the exterior. Construction lasts from four +and one-half to five days.</p> + +<p>9. The nest is compact, pendant, and composed of strips of bark +and strands of grasses that are interwoven and tightly bound with +animal silk. Nests built in May are bulkier than those constructed +later in the season.</p> + +<p>10. Egglaying begins on the first or second day after the nest +is completed. The eggs are deposited early in the morning. The +average clutch-size of the Bell Vireo in Kansas is 3.39 eggs.</p> + +<p>11. Both sexes sit on the eggs, but only the female truly incubates +because the male lacks a brood patch. Incubation lasts fourteen +days.</p> + +<p>12. The Bell Vireo is double-brooded in "good" years.</p> + +<p>13. Nesting failure resulted from severe weather, predation, +parasitism by cowbirds, and human interference. Behavior that +contributes to nesting failure is selection of an unfavorable nest-site, +singing on and near the nest, and the tendency to flush from the nest +in view of potential enemies.</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_294" id="Page_294">[Pg 294]</a></span></p> +<h2><a name="LITERATURE_CITED" id="LITERATURE_CITED"></a>LITERATURE CITED</h2> + + +<div class="blockquot"> +<p><span class="smcap">American Ornithologists' Union</span></p> +<p> 1957. Check-list of North American birds. Fifth ed. Baltimore, The Lord +Baltimore Press, The American Ornithologists' Union, iv + 691 pp.</p> + +<p><span class="smcap">Andrew, R. J.</span></p> +<p> 1956. Intention movements of flight in certain passerines, and their use +in systematics. Behaviour, 10:79-204.</p> + +<p><span class="smcap">Bailey, R. E.</span></p> +<p> 1952. The incubation patch of passerine birds. Condor, 54:121-136.</p> + +<p><span class="smcap">Bennett, W. W.</span></p> +<p> 1917. Bell's Vireo studies (Vireo bellii Aud.). Proc. Iowa Acad. Sci., +24:285-293.</p> + +<p><span class="smcap">Bent, A. C.</span></p> +<p> 1950. Life histories of North American wagtails, shrikes, vireos and their +allies. Smithsonian Inst., U. S. Nat. Mus. Bull., 197:vii + 411 pp., +48 pls.</p> + +<p><span class="smcap">Bunker, C. D.</span></p> +<p> 1910. Habits of the Black-capt Vireo (Vireo atricapillus). Condor, +12:70-73.</p> + +<p><span class="smcap">Chapin, E. A.</span></p> +<p> 1925. Food habits of the vireos; a family of insectivorous birds. U. S. +Dept. Agric. Bull., 1355:1-44.</p> + +<p><span class="smcap">Common, M. A.</span></p> +<p> 1934. Notes on a Red-eyed Vireo's nest. Auk, 51:241-242.</p> + +<p><span class="smcap">Cooke, W. W.</span></p> +<p> 1909. The migration of vireos. Bird Lore, 11:78-82, 118-120, 165-168.</p> + +<p><span class="smcap">Fitch, H. S.</span></p> +<p> 1958. Home ranges, territories and seasonal movements of vertebrates of +the Natural History Reservation. Univ. of Kansas Publ. Mus. of +Nat. Hist., 11:3:63-326.</p> + +<p><span class="smcap">Friedmann, H.</span></p> +<p> 1929. The Cowbirds. Charles C. Thomas, Springfield, Illinois, xviii + +421 pp.</p> + +<p><span class="smcap">Goss, N. S.</span></p> +<p> 1891. History of the birds of Kansas. Topeka, Geo. W. Crane & Co. +Printers and Binders. 692 pp.</p> + +<p><span class="smcap">Graber, R. R.</span></p> +<p> 1955. Artificial incubation of some non-galliform eggs. Wilson Bull., +67:100-109.</p> + +<p><span class="smcap">Hamilton, T. H.</span></p> +<p> 1958. Adaptive variation in the genus Vireo. Wilson Bull., 70:307-346.</p> + +<p><span class="smcap">Hauser, D. C.</span></p> +<p> 1957. Some observations on sun-bathing in birds. Wilson Bull., 69:78-90.</p> +<p> 1959. Notes on pairing and nestbuilding of mismatched vireos. Wilson +Bull., 71:383-384.</p> + +<p><span class="smcap">Hensley, Max</span></p> +<p> 1950. Notes on the breeding behavior of the Bell's Vireo. Auk, 67:243-244.</p> +<p><span class='pagenum'><a name="Page_295" id="Page_295">[Pg 295]</a></span></p> +<p><span class="smcap">Hinde, R. A.</span></p> +<p> 1952. The behaviour of the Great Tit (Parus major) and some other related +species. Leiden: E. J. Brill, x + 201 pp.</p> +<p> 1956. The biological significance of the territories of birds, Ibis, +98:340-369.</p> + +<p><span class="smcap">Hinde, R. A.,</span> and <span class="smcap">Tinbergen, N.</span></p> +<p> 1958. The comparative study of species-specific behavior. In Behavior +and Evolution (Yale University Press, New Haven), pp. 251-268.</p> + +<p><span class="smcap">Kluijver, H. N.</span></p> +<p> 1951. The population ecology of the great tit, Parus m. major L. Ardea, +39:1-135.</p> + +<p><span class="smcap">Lack, D.</span></p> +<p> 1947. The significance of clutch-size. Ibis, 89:302-352.</p> + +<p><span class="smcap">Lawrence, L. de K.</span></p> +<p> 1953. Nesting life and behavior of the Red-eyed Vireo. Can. Field-Nat., +67:46-77.</p> + +<p><span class="smcap">Lewis, H. F.</span></p> +<p> 1921. A nesting of the Philadelphia Vireo. Auk, 38:26-44, 185-202.</p> + +<p><span class="smcap">Linsdale, J. M.</span></p> +<p> 1928. Birds of a limited area in eastern Kansas. The Univ. of Kansas, +Sci. Bull., 18:11:517-626.</p> + +<p><span class="smcap">Lloyd, W.</span></p> +<p> 1887. Birds of Tom Green and Concho Counties, Texas. Auk, 4:181-193, +289-299.</p> + +<p><span class="smcap">Morris, D.</span></p> +<p> 1956. The feather postures of birds and the problem of the origin of social +signs. Behaviour, 9:75-113.</p> + +<p><span class="smcap">Moynihan, M.</span></p> +<p> 1955. Types of hostile display. Auk, 72:247-259.</p> + +<p><span class="smcap">Mumford, R. E.</span></p> +<p> 1952. Bell's Vireo in Indiana. Wilson Bull., 64:224-233.</p> + +<p><span class="smcap">Nice, M. M.</span></p> +<p> 1929. The fortunes of a pair of Bell Vireos. Condor, 31:13-20.</p> +<p> 1943. Studies in the life history of the song sparrow. II. The behavior +of the song sparrow and other passerines. Trans. Linn. Soc. N.Y., 6:328 pp.</p> +<p> 1954. Problems of incubation periods in North American birds. Condor, +56:173-197.</p> + +<p><span class="smcap">Nolan, V.</span></p> +<p> 1960. Breeding behavior of the Bell Vireo in southern Indiana. Condor, +62:225-244.</p> + +<p><span class="smcap">Pitelka, F. A.</span></p> +<p> 1959. Numbers, breeding schedule, and territoriality in Pectoral Sandpipers +of northern Alaska. Condor, 61:223-264.</p> + +<p><span class="smcap">Pitelka, F. A.,</span> and <span class="smcap">Koestner, E. J.</span></p> +<p> 1942. Breeding behavior of Bell's Vireo in Illinois. Wilson Bull., +54:97-106.</p> +<p><span class='pagenum'><a name="Page_296" id="Page_296">[Pg 296]</a></span></p> +<p><span class="smcap">Ridgway, R.</span></p> +<p> 1889. The ornithology of Illinois. Illinois State Nat. Hist. Survey, 1: +viii + 520 pp.</p> +<p> 1904. The birds of North and Middle America. U.S. Nat. Mus. Bull., +50, pt. 3; xx + 801 pp.</p> + +<p><span class="smcap">Skutch, A. F.</span></p> +<p> 1957. The incubation patterns of birds. Ibis, 99:69-93.</p> + +<p><span class="smcap">Southern, W. E.</span></p> +<p> 1958. Nesting of the Red-eyed Vireo in the Douglas Lake Region, Michigan. +The Jack-Pine Warbler, 36:105-130, 185-207.</p> + +<p><span class="smcap">Sutton, G. M.</span></p> +<p> 1949. Studies of the nesting birds of the Edwin S. George Reserve. Part 1. +The Vireos. Misc. Pub. Univ. Michigan Mus. Zool., 74:5-36.</p> + +<p><span class="smcap">Townsend, C. W.</span></p> +<p> 1920. Supplement to the birds of Essex County, Massachusetts. Mem. +Nuttall Orn. Club, No. 5:196 pp.</p> + +<p><span class="smcap">Tyler, W. M.</span></p> +<p> 1912. A vireo courtship. Bird Lore, 14:229-230.</p> + +<p><span class="smcap">Van Tyne, J.</span>, and <span class="smcap">Berger, A. J.</span></p> +<p> 1959. Fundamentals of ornithology. John Wiley & Sons, Inc., New York. +xi + 624 pp.</p> + +<p><span class="smcap">Wetherbee, D. K.</span></p> +<p> 1957. Natal plumages and downy pteryloses of passerine birds of North +America. Bull. Amer. Mus. Nat. Hist., 113:5:339-436.</p></div> + +<p> <i>Transmitted November 8, 1961.</i></p> + +<h5>29-1506</h5> + + +<hr style="width: 65%;" /> +<h2>UNIVERSITY OF KANSAS PUBLICATIONS<br /> +MUSEUM OF NATURAL HISTORY</h2> + + +<p>Institutional libraries interested in publications exchange may obtain +this series by addressing the Exchange Librarian, University of Kansas +Library, Lawrence, Kansas. Copies for individuals, persons working in +a particular field of study, may be obtained by addressing instead the +Museum of Natural History, University of Kansas, Lawrence, Kansas. +There is no provision for sale of this series by the University +Library, which meets institutional requests, or by the Museum of +Natural History, which meets the requests of individuals. However, +when individuals request copies from the Museum, 25 cents should be +included, for each separate number that is 100 pages or more in +length, for the purpose of defraying the costs of wrapping and +mailing.</p> + +<p>* An asterisk designates those numbers of which the Museum's supply +(not the Library's supply) is exhausted. Numbers published to date, in +this series, are as follows:</p> + +<div class="blockquot"> +<p>Vol. 1. Nos. 1-26 and index. Pp. 1-638, 1946-1950.</p> + +<p>*Vol. 2. (Complete) Mammals of Washington. By Walter W. Dalquest. Pp. +1-444, 140 figures in text. April 9, 1948.</p> + +<p>Vol. 3. *1. The avifauna of Micronesia, its origin, evolution, and +distribution. By Rollin H. Baker. Pp. 1-359, 16 figures in text. June +12, 1951.<br /> +<br /> +*2. A quantitative study of the nocturnal migration of birds. By +George H. Lowery, Jr. Pp. 361-472, 47 figures in text. June 29, 1951.<br /> +<br /> +3. Phylogeny of the waxwings and allied birds. By M. Dale Arvey. Pp. +473-530, 49 figures in text, 13 tables. October 10, 1951.<br /> +<br /> +4. Birds from the state of Veracruz, Mexico. By George H. Lowery, Jr., +and Walter W. Dalquest. Pp. 531-649, 7 figures in text, 2 tables. +October 10, 1951.<br /> +<br /> +Index. Pp. 651-681.</p> + +<p>*Vol 4. (Complete) American weasels. By E. Raymond Hall. Pp. 1-466, +41 plates, 31 figures in text. December 27, 1951.</p> + +<p>Vol. 5. Nos. 1-37 and index. Pp. 1-676, 1951-1953.</p> + +<p>*Vol 6. (Complete) Mammals of Utah, <i>taxonomy and distribution</i>. By +Stephen D. Durrant. Pp. 1-549, 91 figures in text, 30 tables. August +10, 1952.</p> + +<p>Vol. 7. *1. Mammals of Kansas. By E. Lendell Cockrum. Pp. 1-303, 73 +figures in text, 37 tables. August 25, 1952.<br /> +<br /> +2. Ecology of the opossum on a natural area in northeastern Kansas. By +Henry S. Fitch and Lewis L. Sandidge. Pp. 305-338, 5 figures in text. +August 24, 1953.<br /> +<br /> +3. The silky pocket mice (Perognathus flavus) of Mexico. By Rollin H. +Baker. Pp. 339-347, 1 figure in text. February 15, 1954.<br /> +<br /> +4. North American jumping mice (Genus Zapus). By Phillip H. Krutzsch. +Pp. 349-472, 47 figures in text, 4 tables. April 21, 1954.<br /> +<br /> +5. Mammals from Southeastern Alaska. By Rollin H. Baker and James S. +Findley. Pp. 473-477. April 21, 1954.<br /> +<br /> +6. Distribution of Some Nebraskan Mammals. By J. Knox Jones, Jr. Pp. +479-487. April 21, 1954.<br /> +<br /> +7. Subspeciation in the montane meadow mouse, Microtus montanus, in +Wyoming and Colorado. By Sydney Anderson. Pp. 489-506, 2 figures in +text. July 23, 1954.<br /> +<br /> +8. A new subspecies of bat (Myotis velifer) from southeastern +California and Arizona. By Terry A. Vaughan. Pp. 507-512. July 23, +1954.<br /> +<br /> +9. Mammals of the San Gabriel mountains of California. By Terry A. +Vaughan. Pp. 513-582, 1 figure in text, 12 tables. November 15, 1954.<br /> +<br /> +10. A new bat (Genus Pipistrellus) from northeastern Mexico. By Rollin +H. Baker. Pp. 583-586. November 15, 1954.<br /> +<br /> +11. A new subspecies of pocket mouse from Kansas. By E. Raymond Hall. +Pp. 587-590. November 15, 1954.<br /> +<br /> +12. Geographic variation in the pocket gopher, Cratogeomys castanops, +in Coahuila, Mexico. By Robert J. Russell and Rollin H. Baker. Pp. +591-608. March 15, 1955.<br /> +<br /> +13. A new cottontail (Sylvilagus floridanus) from northeastern Mexico. +By Rollin H. Baker. Pp. 609-612. April 8, 1955.<br /> +<br /> +14. Taxonomy and distribution of some American shrews. By James S. +Findley. Pp. 613-618. June 10, 1955.<br /> +<br /> +15. The pigmy woodrat, Neotoma goldmani, its distribution and +systematic position. By Dennis G. Rainey and Rollin H. Baker. +Pp. 619-624. 2 figures in text. June 10, 1955.<br /> +<br /> +Index. Pp. 625-651.</p> + +<p>Vol. 8. Nos. 1-10 and index. Pp. 1-675, 1954-1956.</p> + +<p>Vol. 9. 1. Speciation of the wandering shrew. By James S. Findley. Pp. +1-68, 18 figures in text. December 10, 1955.<br /> +<br /> +2. Additional records and extension of ranges of mammals from Utah. By +Stephen D. Durrant, M. Raymond Lee, and Richard M. Hansen. Pp. 69-80. +December 10, 1955.<br /> +<br /> +3. A new long-eared myotis (Myotis evotis) from northeastern Mexico. +By Rollin H. Baker and Howard J. Stains. Pp. 81-84. December 10, 1955.<br /> +<br /> +4. Subspeciation in the meadow mouse, Microtus pennsylvanicus, in +Wyoming. By Sydney Anderson. Pp. 85-104, 2 figures in text. May 10, +1956.<br /> +<br /> +5. The condylarth genus Ellipsodon. By Robert W. Wilson. Pp. 105-116, +6 figures in text. May 19, 1956.<br /> +<br /> +6. Additional remains of the multituberculate genus Eucosmodon. By +Robert W. Wilson. Pp. 117-123, 10 figures in text. May 19, 1956.<br /> +<br /> +7. Mammals of Coahuila, Mexico. By Rollin H. Baker. Pp. 125-335, 75 +figures in text. June 15, 1956.<br /> +<br /> +8. Comments on the taxonomic status of Apodemus peninsulae, with +description of a new subspecies from North China. By J. Knox Jones, +Jr. Pp. 337-346, 1 figure in text, 1 table. August 15, 1956.<br /> +<br /> +9. Extensions of known ranges of Mexican bats. By Sydney Anderson. Pp. +347-351. August 15, 1956.<br /> +<br /> +10. A new bat (Genus Leptonycteris) from Coahuila. By Howard J. +Stains. Pp. 353-356. January 21, 1957.<br /> +<br /> +11. A new species of pocket gopher (Genus Pappogeomys) from Jalisco, +Mexico. By Robert J. Russell. Pp. 357-361. January 21, 1957.<br /> +<br /> +12. Geographic variation in the pocket gopher, Thomomys bottae, in +Colorado. By Phillip M. Youngman. Pp. 363-387, 7 figures in text. +February 21, 1958.<br /> +<br /> +13. New bog lemming (genus Synaptomys) from Nebraska. By J. Knox +Jones, Jr. Pp. 385-388. May 12, 1958.<br /> +<br /> +14. Pleistocene bats from San Josecito Cave, Nuevo León, México. By J. +Knox Jones, Jr. Pp. 389-396. December 19, 1958.<br /> +<br /> +15. New subspecies of the rodent Baiomys from Central America. By +Robert L. Packard. Pp. 397-404. December 19, 1958.<br /> +<br /> +16. Mammals of the Grand Mesa, Colorado. By Sydney Anderson. Pp. +405-414, 1 figure in text, May 20, 1959.<br /> +<br /> +17. Distribution, variation, and relationships of the montane vole, +Microtus montanus. By Sydney Anderson. Pp. 415-511, 12 figures in +text, 2 tables. August 1, 1959.<br /> +<br /> +18. Conspecificity of two pocket mice, Perognathus goldmani and P. +artus. By E. Raymond Hall and Marilyn Bailey Ogilvie. Pp. 513-518, 1 +map. January 14, 1960.<br /> +<br /> +19. Records of harvest mice, Reithrodontomys, from Central America, +with description of a new subspecies from Nicaragua. By Sydney +Anderson and J. Knox Jones, Jr. Pp. 519-529. January 14, 1960.<br /> +<br /> +20. Small carnivores from San Josecito Cave (Pleistocene), Nuevo León, +México. By E. Raymond Hall. Pp. 531-538, 1 figure in text. January 14, +1960.<br /> +<br /> +21. Pleistocene pocket gophers from San Josecito Cave, Nuevo León, +México. By Robert J. Russell. Pp. 539-548, 1 figure in text. January +14, 1960.<br /> +<br /> +22. Review of the insectivores of Korea. By J. Knox Jones, Jr., and +David H. Johnson. Pp. 549-578. February 23, 1960.<br /> +<br /> +23. Speciation and evolution of the pygmy mice, genus Baiomys. By +Robert L. Packard. Pp. 579-670, 4 plates, 12 figures in text. June 16, +1960.<br /> +<br /> +Index. Pp. 671-690.</p> + +<p>Vol. 10. 1. Studies of birds killed in nocturnal migration. By +Harrison B. Tordoff and Robert M. Mengel. Pp. 1-44, 6 figures in text, +2 tables. September 12, 1956.<br /> +<br /> +2. Comparative breeding behavior of +Ammospiza caudacuta and A. maritima. By Glen E. Woolfenden. Pp. 45-75, +6 plates, 1 figure. December 20, 1956.<br /> +<br /> +3. The forest habitat of the University of Kansas Natural History +Reservation. By Henry S. Fitch and Ronald R. McGregor. Pp. 77-127, 2 +plates, 7 figures in text, 4 tables. December 31, 1956.<br /> +<br /> +4. Aspects of reproduction and development in the prairie vole +(Microtus ochrogaster). By Henry S. Fitch. Pp. 129-161, 8 figures in +text, 4 tables. December 19, 1957.<br /> +<br /> +5. Birds found on the Arctic slope of northern Alaska. By James W. +Bee. Pp. 163-211, plates 9-10, 1 figure in text. March 12, 1958.<br /> +<br /> +6. The wood rats of Colorado: distribution and ecology. By Robert B. +Finley, Jr. Pp. 213-552, 34 plates, 8 figures in text, 35 tables. +November 7, 1958.<br /> +<br /> +7. Home ranges and movements of the eastern cottontail in Kansas. By +Donald W. Janes. Pp. 553-572, 4 plates, 3 figures in text. May 4, +1959.<br /> +<br /> +8. Natural history of the salamander, Aneides hardyi. By Richard F. +Johnston and Gerhard A. Schad. Pp. 573-585. October 8, 1959.<br /> +<br /> +9. A new subspecies of lizard, Cnemidophorus sacki, from Michoacán, +México. By William E. Duellman, Pp. 587-598, 2 figures in text. May 2, +1960.<br /> +<br /> +10. A taxonomic study of the middle American snake, Pituophis deppei. +By William E. Duellman. Pp. 599-610, 1 plate, 1 figure in text. May 2, +1960.<br /> +<br /> +Index. Pp. 611-626.</p> + +<p>Vol. 11. 1. The systematic status of the colubrid snake, Leptodeira +discolor Günther. By William E. Duellman. Pp. 1-9, 4 figures. July 14, +1958.<br /> +<br /> +2. Natural history of the six-lined racerunner, Cnemidophorus +sexlineatus. By Henry S. Fitch. Pp. 11-62, 9 figures, 9 tables. +September 19, 1958.<br /> +<br /> +3. Home ranges, territories, and seasonal movements of vertebrates of +the Natural History Reservation. By Henry S. Fitch. Pp. 63-326, 6 +plates, 24 figures in text, 3 tables. December 12, 1958.<br /> +<br /> +4. A new snake of the genus Geophis from Chihuahua, Mexico. By John M. +Legler. Pp. 327-334, 2 figures in text. January 28, 1959.<br /> +<br /> +5. A new tortoise, genus Gopherus, from north-central Mexico. By John +M. Legler. Pp. 335-343. April 24, 1959.<br /> +<br /> +6. Fishes of Chautauqua, Cowley and Elk counties, Kansas. By Artie L. +Metcalf. Pp. 345-400, 2 plates, 2 figures in text, 10 tables. May 6, +1959.<br /> +<br /> +7. Fishes of the Big Blue river basin, Kansas. By W. L. Minckley. Pp. +401-442. 2 plates, 4 figures in text, 5 tables. May 8, 1959.<br /> +<br /> +8. Birds from Coahuila, México. By Emil K. Urban. Pp. 443-516. August +1, 1959.<br /> +<br /> +9. Description of a new softshell turtle from the southeastern United +States. By Robert G. Webb. Pp. 517-525, 2 plates, 1 figure in text. +August 14, 1959.<br /> +<br /> +10. Natural history of the ornate box turtle, Terrapene ornata ornata +Agassiz. By John M. Legler. Pp. 527-669, 16 pls., 29 figures in text. +March 7, 1960.<br /> +<br /> +Index Pp. 671-703.</p> + +<p>Vol. 12. 1. Functional morphology of three bats: Eumops, Myotis, +Macrotus. By Terry A. Vaughan. Pp. 1-153, 4 plates, 24 figures in +text. July 8, 1959.<br /> +<br /> +2. The ancestry of modern Amphibia: a review of the evidence. By +Theodore H. Eaton, Jr. Pp. 155-180, 10 figures in text. July 10, 1959.<br /> +<br /> +3. The baculum in microtine rodents. By Sydney Anderson. Pp. 181-216, +49 figures in text. February 19, 1960.<br /> +<br /> +4. A new order of fishlike Amphibia from the Pennsylvanian of Kansas. +By Theodore H. Eaton, Jr., and Peggy Lou Stewart. Pp. 217-240, 12 +figures in text. May 2, 1960.<br /> +<br /> +5. Natural history of the bell vireo. By Jon C. Barlow. Pp. 241-296, 6 +figures in text. March 7, 1962.<br /> +<br /> +More numbers will appear in volume 12.</p> + +<p>Vol. 13. 1. Five natural hybrid combinations in minnows (Cyprinidae). +By Frank B. Cross and W. L. Minckley. Pp. 1-18. June 1, 1960.<br /> +<br /> +2. A distributional study of the amphibians of the Isthmus of +Tehuantepec, México. By William E. Duellman. Pp. 19-72, pls. 1-8, 3 +figures in text. August 16, 1960.<br /> +<br /> +3. A new subspecies of the slider turtle (Pseudemys scripta) from +Coahuila, México. By John M. Legler. Pp. 73-84, pls. 9-12, 3 figures +in text. August 16, 1960.<br /> +<br /> +4. Autecology of the copperhead. By Henry S. Fitch. Pp. 85-288, pls. +13-20, 26 figures in text. November 30, 1960.<br /> +<br /> +5. Occurrence of the garter snake, Thamnophis sirtalis, in the Great +Plains and Rocky Mountains. By Henry S. Fitch and T. Paul Maslin. Pp. +289-308, 4 figures in text. February 10, 1961.<br /> +<br /> +6. Fishes of the Wakarusa river in Kansas. By James E. Deacon and +Artie L. Metcalf. Pp. 309-322, 1 figure in text. February 10, 1961.<br /> +<br /> +7. Geographic variation in the North American cyprinid fish. Hybopsis +gracilis. By Leonard J. Olund and Frank B. Cross. Pp. 323-348, pls. +21-24, 2 figures in text. February 10, 1961.<br /> +<br /> +8. Descriptions of two species of frogs, genus Ptychohyla; studies of +American hylid frogs, V. By William E. Duellman. Pp. 349-357, pl. 25, +2 figures in text. April 27, 1961.<br /> +<br /> +9. Fish populations, following a drought, in the Neosho and Marais des +Cygnes rivers of Kansas. By James Everett Deacon. Pp. 359-427, pls. +26-30, 3 figs. August 11, 1961.<br /> +<br /> +10. Recent soft-shelled turtles of North America (family +Trionychidae). By Robert G. Webb. Pp. 429-611, pls. 31-54, 24 figures +in text. February 16, 1962.</p> + +<p>Vol. 14. 1. Neotropical bats from western México. By Sydney Anderson. +Pp. 1-8. October 24, 1960.<br /> +<br /> +2. Geographic variation in the harvest mouse, Reithrodontomys +megalotis, on the central Great Plains and in adjacent regions. By J. +Knox Jones, Jr., and B. Morsaloglu. Pp. 9-27, 1 figure in text. July +24, 1961.<br /> +<br /> +3. Mammals of Mesa Verde National Park, Colorado. By Sydney Anderson. +Pp. 29-67, pls. 1 and 2, 3 figures in text. July 24, 1961.<br /> +<br /> +4. A new subspecies of the black myotis (bat) from eastern Mexico. By +E. Raymond Hall and Ticul Alvarez. Pp. 69-72, 1 figure in text. +December 29, 1961.<br /> +<br /> +5. North American yellow bats, "Dasypterus," and a list of the named +kinds of the genus Lasiurus Gray. By E. Raymond Hall and J. Knox +Jones, Jr. Pp. 73-98, 4 figures in text. December 29, 1961.<br /> +<br /> +6. Natural history of the brush mouse (Peromyscus boylii) in Kansas +with description of a new subspecies. By Charles A. Long. Pp. 99-111, +1 figure in text. December 29, 1961.<br /> +<br /> +7. Taxonomic status of some mice of the Peromyscus boylii group in +eastern Mexico, with description of a new subspecies. By Ticul +Alvarez. Pp. 113-120, 1 figure in text. December 29, 1961.<br /> +<br /> +8. A new subspecies of ground squirrel (Spermophilus spilosoma) from +Tamaulipas, Mexico. By Ticul Alvarez. Pp. 121-124. March 7, 1962.<br /> +<br /> +9. Taxonomic status of the free-tailed bat, Tadarida yucatanica +Miller. By J. Knox Jones, Jr., and Ticul Alvarez. Pp. 125-133, 1 +figure in text. March 7, 1962.<br /> +<br /> +More numbers will appear in volume 14.</p> + +<p>Vol. 15. 1. The amphibians and reptiles of Michoacán, México. By +William E. Duellman. Pp. 1-148, pls. 1-6, 11 figures in text. December +20, 1961.<br /> +<br /> +2. Some reptiles and amphibians from Korea. By Robert G. Webb, J. Knox +Jones, Jr., and George W. Byers. Pp. 149-173. January 31, 1962.<br /> +<br /> +3. A new species of frog (Genus Tomodactylus) from western México. By +Robert G. Webb. Pp. 175-181, 1 figure in text. March 7, 1962.<br /> +<br /> +More numbers will appear in volume 15.</p></div> + + + + + + + + + +<pre> + + + + + +End of the Project Gutenberg EBook of Natural History of the Bell Vireo, +Vireo bellii Audubon, by Jon C. Barlow + +*** END OF THIS PROJECT GUTENBERG EBOOK THE BELL VIREO *** + +***** This file should be named 32855-h.htm or 32855-h.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/3/2/8/5/32855/ + +Produced by Chris Curnow, Joseph Cooper and the Online +Distributed Proofreading Team at http://www.pgdp.net + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. Special rules, +set forth in the General Terms of Use part of this license, apply to +copying and distributing Project Gutenberg-tm electronic works to +protect the PROJECT GUTENBERG-tm concept and trademark. 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