The person charging this material is re- sponsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN JUN 1 1 IS JUN 1 4 197* ILLINOIS BIOLOGICAL MONOGRAPHS Volume XVIII PUBLISHED BY THE UNIVERSITY OF ILLINOIS URBANA, ILLINOIS Digitized by the Internet Archive in 2011 with funding from University of Illinois Urbana-Champaign http://www.archive.org/details/territorialmatin183kend ILLINOIS BIOLOGICAL MONOGRAPHS Vol. XVIII No. 3 Published by the University of Illinois Under the Auspices of the Graduate School Urbana, Illinois EDITORIAL COMMITTEE John Theodore Buchholz Fred Wilbur Tanner Harley Jones Van Cleave 1000—6-41—21151 TERRITORIAL AND MATING BEHAVIOR OF THE HOUSE WREN WITH 32 FIGURES BY S. Charles Kendeigh Contribution from the Baldwin Bird Research Laboratory No. 37 and from the zoological laboratory of the University of Illinois No. 582 THE UNIVERSITY OF ILLINOIS PRESS URBANA 1941 u CONTENTS I. Introduction 7 II. Spring Arrival of Birds 12 Integration of the Breeding Population 13 Return to Former Territories 15 Homing Tendency in Nesting Birds 19 III. Establishment and Defense of Territories ... 20 Song 20 Nest-sites 23 Chasing and Fighting 25 Evolution of Territorial Defense 27 Destructive Tendencies 28 The Female's Role 35 IV. Characteristics of the Territory 36 Variability in Territorial Boundaries 36 Changes in Territories between Breeding Periods ... 37 Size of Territories 39 V. Reproductive Vigor 44 Physiological Readiness 44 Non-Breeders 44 Multiple Nesting 46 VI. Mating Behavior 48 Nest Inspection and Courtship 48 Coition 50 Female Discriminations 51 Sex Recognition 51 Remating for Second Breeding Period 53 Remating in Subsequent Seasons 54 VII. Termination of Nesting 57 VIII. History of Individual Territories 59 IX. History of Individual Birds 110 X. Summary 116 XI. Literature Cited 119 ACKNOWLEDGMENT The work reported in this paper is by no means the contribution of any- one person. The greatest credit is due to the late Dr. S. Prentiss Baldwin, who not only financed the entire undertaking but also had the early vision and energy to initiate this study and to direct its continuance. He person- ally made all the observations and notes through 1924, and he participated whole-heartedly in the work thereafter until his death in 1938. My own attention to this problem covers the period from 1925 to 1939, inclusive. Many assistants and associates participated in collecting data, and I am pleased to list their names and the seasons when they worked at the Baldwin Bird Research Laboratory: Rudyerd Boulton, 1926 Carl M. Johnson, 1931-1934 W. Wedgwood Bowen, 1927 Roscoe W. Franks, 1932 Ross B. Albaugh, 1928-1929 Wilbur S. Long, 1935 Leonard G. Worley, 1928-1930 James Bruce, 1935 Theodore C. Kramer, 1929-1934 Eugene P. Odum, 1936-1938 Mae MacNab, 1929-1938 Russell A. Huggins, 1936-1938 Delos Johnson, 1930 Irene T. Rorimer, 1937 James Stevenson, 1930-1931 Sarah E. Huggins, 1937-1938 Francis Gilliland, 1931 Frank A. Pitelka, 1939 I take pleasure in acknowledging the helpful comments and criticisms made by Dr. Ernst Mayr and Dr. A. L. Rand, both of the American Museum of Natural History, who read this paper in manuscript form. I am grateful also to Mr. J. Murray Speirs for suggesting the method used in the drawings to show T territories each year. I. INTRODUCTION The requirements and behavior of the house wren. Troglodytes aedon, in respect to territory are similar to those described by Howard (1920, 1929) for several passerine species. In the following discussion it will be apparent how the behavior of the house wren (Fig. 1) satisfies the definition given by Howard (1929, p. 63) that "when territory is im- perative, a male isolates himself, makes himself conspicuous, becomes intolerant of other males, and exercises dominion over a definite area." Territory is generally considered as important in various ways: as a means by which birds become paired and mated, as an insurance of adequate nest-sites and food supply for adults and young, and as a safeguard against disturbance. The process of courtship and mating can scarcely be separated in the house wren from the phenomena of territory, as they are so vitally interwoven and intrinsically related. There is considerable literature on the life-history and behavior of the house wren. A bibliography including every mention of information dealing with territory, mating, interrelations, and nesting in this species would run into dozens of references. As very few of them tend to tell the whole story, citations will be made only when they have a direct bearing on topics considered in the following pages, although for a general background the following references may be consulted: Wright (1909), Baldwin (1921), Sherman (1925), and Allen (1927). Likewise the study of territory in the St. Kilda wren, Troglodytes t. hirtensis, by Harrisson and Buchan (1934) has a direct relation, as does the recent life-history study of the European wren, Troglodytes t. troglodytes, by Kluijver et al (1940). References for comparative purposes will be made to these wrens and to the long-billed marsh wren, Telmatodytes palustris, that was studied by Welter (1935), but otherwise no attempt will be made at a monographic treatment of territorial and mating behavior as it applies to birds in general. Since this paper was written, an article by Miller (1941) dealing with the Bewick wren, Thryomanes bezvickii, has appeared. Items in the be- havior of this wren of special interest for comparison with the other members of this family discussed in the following pages are here briefly summarized. This species of the southern United States has several sub- species, some being migratory, as T. b. bezvickii, but others, as 7". b. spilnrus in California, which received major attention, being permanent residents. The latter, at least some more mature individuals, maintain a territory throughout the year, although less vigorously during the winter. Defense of territory appears to be entirely by song. Only the male sings, and the singing period lasts from early spring to late autumn. The female 8 ILLINOIS BIOLOGICAL MONOGRAPHS takes no part in the territorial relations, although she appears to be cognizant of the boundaries of the territory belonging to her mate and does not venture outside. The territories average about an acre (0.4 hectare) in size. Mating occurs in early spring; the sexual status of paired birds frequently observed in winter is uncertain. Individuals recognize each other's sex by differences in call-notes and by the male's song. The female has special notes that serve as an invitation to the male for copulation. Two broods are raised during the season. Both sexes share in nest-building ; the nests are placed in tree cavities ; and pieces of snake skin are often incorporated in the nest-material. Although the male may start several nests, the possession of multiple nests is not a charac- teristic trait of this species as in some other members of this family. Although the male does not incubate, he is closely attentive, frequently feeding the female on the nest or elsewhere and sharing in the care of the young. The study here reported covers the nineteen-year period from 1921 to 1939, inclusive, at the Baldwin Bird Research Laboratory, near Cleve- land, Ohio. Perhaps the study actually began considerably earlier, for in Dr. S. Prentiss Baldwin's 1919 paper on the "marriage relations of the house wren," in which he reported on studies initiated in 1914, he tells how male birds sing and begin nest-building and compete with other males for the possession of nest-sites. Dr. Baldwin often stated that his notes were "full of territory," yet their significance as such did not appear until he had read Howard's classic study in 1920. Since 1921, detailed obser- vations are available and are here summarized on the territorial behavior of 142 male and 147 female birds. Since many of these birds returned to the area year after year or had two broods in the same year, altogether some 331 matings between males and females are recorded, each mating the climax and goal of an individual territorial maneuver. This is the nineteen-year population on the "Hillcrest" area (Fig. 2). Altogether, the history of 215 individual male territories enter into this study. Many observations made in the "Outfield" area are also included as they bear on particular points. The Hillcrest area (Fig. 3) included the fifteen acres immediately around the former home of Dr. and Mrs. Baldwin and at the top of the west bluff of the Chagrin River Valley. On the north the study area merged into hard maple-beech woods that extended fairly continuously for several miles beyond. The boundary on the east contacted several acres of cultivated land and pasture transversed by a wild rose lane and scattered trees and shrubs. Another estate of similar composition lay to the south, and extensive shrubby pastures adjoined to the west. On the fifteen acres (six hectares) of the Hillcrest area itself, besides several buildings and long driveways, there were flower and vegetable Fig. 1. — House wren standing on trap-door perch at nest-box. Note the celluloid band around the riarht leg of the bird. Fig. 2. — Air-view of Hillcrest area looking west. Mayfield Road on the left marks the south boundary, and West Hill Drive, extending to the right near the top, marks the west boundary. The fence in the lower right corner is the eastern limit of the area. The hard maple grove is in the upper right corner. The barns and north edge of the area are not shown. Other features of the area may be identified from Fig. 3. o c , bfl -i en tn cr 3 CU ^^ J5 i/) £ CJ CI -1 — i-l en co 0J O 3 O 1 o u CM = r °^ "^ -; w c fci °° CO u fe