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UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY

Volume 12, No. 5, pp. 241-296, 6 figs. March 7, 1962

Natural History of the Bell Vireo, Vireo bellii Audubon

BY JON C. BARLOW

UNIVERSITY OF KANSAS LAWRENCE 1962

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Theodore H. Eaton, Jr., Henry S. Fitch

Volume 12, No. 5, pp. 241-296, 6 figs. Published March 7, 1962

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED BY JEAN M. NEIBARGER, STATE PRINTER TOPEKA, KANSAS 1962

29-1506

Natural History of the Bell Vireo, Vireo bellii Audubon

JON C. BARLOW

CONTENTS

PAGE CONTENTS 243 INTRODUCTION 245 ACKNOWLEDGMENTS 245 METHODS OF STUDY 246 STUDY AREA 247 Considerations of Habitat 248 SEASONAL MOVEMENT 250 Arrival in Spring 250 Fall Departure 251 GENERAL BEHAVIOR 252 Flight 252 Foraging and Food Habits 252 Bathing 253 VOCALIZATIONS 254 Singing Postures 255 Flight Song 255 Daily Frequency of Song 255 Types of Vocalizations 255 TERRITORIALITY 258 Establishment of Territory 259 Size of Territories 259 Permanence of Territories 260 Maintenance of Territory 260 Aggressive Behavior of the Female 264 Interspecific Relationships 264 Discussion 265 COURTSHIP BEHAVIOR 267 Displays and Postures 268 Discussion 270 SELECTION OF NEST-SITE AND NESTBUILDING 272 Building 274 Gathering of Nesting Materials 276 Length and Hours of Nestbuilding 277 Abortive Nestbuilding Efforts 277 Renesting 277 The Nest 277 EGGLAYING AND INCUBATION 278 Egglaying 278 Clutch-size 279 Incubation 280 The Roles of the Sexes in Incubation 280 Relief of Partners in Incubation 283 NESTLING PERIOD 283 Hatching Sequence 283 Development of the Nestlings 284 Parental Behavior 285 Feeding of the Nestlings 286 Nest Sanitation 287 Fledging 287 Nest Parasites 287 FLEDGLING LIFE 288 Second Broods 288 REPRODUCTIVE SUCCESS 289 Behavior 290 Predation 291 Cowbird Parasitism 291 SUMMARY 292 LITERATURE CITED 294

INTRODUCTION

The Bell Vireo (Vireo bellii 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.

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.

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 (Vireo olivaceus) 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.

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.

ACKNOWLEDGMENTS

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 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.

METHODS OF STUDY

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.

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.

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.

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 x 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.