^p^lfffflj^[lj^^j^^^^^^^^^^^^^^^^}^lllgj SMITHSONIAN INSTITUTION UNITED STATES NATIONAL MUSEUM BULLETIN 223 WASHINGTON, D.C. 1960 The Parasitic Weaverbirds By HERBERT FRIEDMANN Head Curator, Department of Zoology- United States National Museum Publications of the United States National Museum The scientific publications of the United States National Museum include two series, Proceedings of the United States National Museum and United States National Museum Bulletin. In these series are published original articles and monographs dealing with the collections and work of the Museum and setting forth newly acquired facts in the fields of Anthropology, Biology, Geology, History, and Technology. Copies of each publication are distributed to libraries and scientific organizations and to specialists and others interested in the different subjects. The Proceedings, begun in 1878, are intended for the publication, in separate form, of shorter papers. 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Price n Contents Page Preface vii Evolution of Brood Parasitism in Weaverbirds 3 Phylogenetic Background 3 Ethological Background 13 Adaptive Features 22 Antiquity 32 Contributive Factors 34 The Species of Parasitic Weaverbirds 39 Cuckoo Finch: Anomalospiza imberbis 39 Short-tailed widow birds: Subgenus Hypochera 55 Brown-Winged Glossy Combassou: Vidua amauropteryx .... 68 Brown-Winged Dusky Combassou: Vidua funerea 75 Black-Winged Combassou: Vidua chalybeata 81 Long-Tailed Widow Birds: Subgenus Vidua 89 Blue Widow Bird: Vidua hypocherina 90 Pin-Tailed Widow Bird: Vidua macroura 93 Straw-Tailed Widow Bird: Vidua fischeri 123 Shaft-Tailed Widow Bird: Vidua regia 127 Paradise Widow Bird: Genus Steganura 136 Paradise Widow Bird: Steganura paradisaea 139 References 161 Index 187 Preface THIS STUDY OF THE PARASITIC WEAVERBiRDS is an entity in itself, complete as far as available data permit. It is also a part of a general survey of the problem of avian brood parasitism, in the course of which, besides many pertinent short papers, monogi^aphs dealing with other families of parasitic birds were issued by me on the cow- birds (1929), on the African cuckoos (1946), and on the honey-guides (1955). To complete the series I hope eventually to publish a com- prehensive comparative and interpretive summation of the biological aspects of the subject. For many years I hesitated to write the present portion of the survey because the available information was fragmentary, and there was little reason to expect that the accounts resulting from this in- formation would lend themselves to clarifying comment. Although new information has been exceedingly slow in coming into print and our present knowledge is still obviously fragmentary, now, after 35 years of patiently watching for such items in the literature, and of extensive correspondence with resident observers in the homelands of the bh'ds involved, in addition to personal fieldwork in Africa, I ven- ture to present the picture, incomplete to be sure, but sufficiently filled in to reveal in general outline the nature of brood parasitism in the weaverbirds. In the first part of this study is presented the evolution of brood parasitism, and in the second the data on which I have based my in- terpretation. The study should, I hope, stimulate observers to supply further data and at the same time expedite their work by directing them to the gaps that I have not been able to close. During the course of my studies, many persons and organizations have assisted me in many ways, all of which contributed to the degree of completeness attained in the following pages. Not that I consider the problems fully worked out or the solutions arrived at as definitive, but I would not have been able to come as far as I have without these contributions. My personal field work in southern and eastern Africa was supported first, in 1924-25, by the National Research Council tlu-ough funds supplied bj^ the Rockefeller Foundation, and later, in 1950-51, by grants from tlio John Shnon Guggenheim Memo- rial Foundation, the American Philosophical Society, and the Smith- sonian Institution. Without the generous support of tlicse sponsoring groups the field work would not have been possible, and the study would not have been undertaken. VIII U.S. NATIONAL MUSEUM BULLETIN 223 It is a pleasure to record my gratitude about the following kind friends, who contributed to the present study either by direct assist- ance or cooperation in the field, or by sending me items from their own largely unpublished observational data: J. P. Chapin, N. E. Collias, M. P. S. Irwin, C. H. Jerome, D. W. Lamm, H. M. Miles, G. Morel, B. V. Neuby-Varty, R. H. W. Pakenham, D. C. H. Plowes, the late C. D. Priest, G. A. Radtke, the late A. Roberts, M. Rollo, C. J. Skead, R. E. Symons, V. G. L. van Someren, and J. G. Williams. H. Poulsen of the Copenhagen Zoological Park aided me with data on aviary observations on combassous. For giving me the opportunity to study specimens in their respective museums, I am indebted to officials of the American Museum of Natural History, New York; British Museum (Natural Historj^), London; Chicago Natural History Museum, Chicago; Coryndon Museum, Nairobi; Durban Museum and Art Gallery, Durban; Kaffrarian Museum, King William's Town; Museum of Comparative Zoology, Cambridge, Mass.; Natal Museum, Pietermaritzburg; National Museum of Southern Rhodesia, Bulawaj^o ; Peabody Museum of Yale University, New Haven, Conn.; Transvaal Museum, Pretoria; and Victoria Memorial Museum, Salisbury. The American Museum of Natural History, the Chicago Natural History Museum, D. C. H. Plowes, and V. G. L. van Someren con- tributed photographs that add appreciably to the illustrations in this report. The John Simon Guggenheim Memorial Foundation made a special grant to cover the costs of the colored plates. To Patricia Hogue, formerly staff artist of the U.S. National Museum, are due my thanks for her work, including plates 2, 9, 11, and 15, and to R. E. Hogue for his three paintings, plates 1, 3, and 4. The Parasitic Weaverbirds Evolution of Brood Parasitism in Weaverhirds THAT PARASITIC REPRODUCTION OCCURS ill the weaverbirds was first made known in 1907 by A. Roberts/ writing about the pin- tailed widow bird, Vidua macroura, in South Africa. Shortly after- ward, Jackson and his native collector, Baraka, made similar observa- tions on this species in East Africa, and subsequently IVIors and V. G. L. van Someren produced still further evidence. Roberts (1917) and van Someren (1918) also reported almost simultaneously that the cuckoo finch, Anomalosjpiza imberbis, was also parasitic. Since then the same habit has been found in other species of Vidua and in the paradise widow bird, Steganura paradisaea. Of not one of these species is our present knowledge more than partial; of some it is still extremel}^ fragmentary. These birds offer the natm'alists resident in Africa a real opportunity for rewarding work. Phylogenetic Background In approaching the problem of the evolution of brood parasitism in viduine weavers and in Anomalospiza, I must first establish a frame of reference on which to peg pertinent data. I must first show where these birds fit in the overall pictm-e of the family and what their ancestry within that group may have been. We are fortunate in having two comprehensive discussions of ploceid taxonomy—'One by Chapin (1917) and one by Sushkin (1927)—the first based on extensive acquaintance with a large number of the included genera and species in life as well as in the museum, and the second couched in terms of the skeletal anatomy of the group. Chapin was the first to use characters such as the pattern of the mouth mark- ings of the nesthngs, the type of nest constructed, and the presence or absence of seasonal plumage changes—all of which have been found to be more revealing of true relationsliips than such overemphasized "museum" characters as the relative length of the outermost primary. Sushkin's conclusions provided complementary information concern- ' At this time there was in the literature an unverified belief that the red-billed weaver, Quelea quelea, might also be a brood parasite. This belief since disproved, was based upon the fact that although the bird was very abundant, no one had found and described its nest. Since then, large breeding colonies have been located and studied in considerable detail. 3 4 U.S. NATIONAL MUSEUM BULLETIN 2 23 ing the degree of similarity or differeDce in the skeletal structure of many of the genera ol the family. In addition to these two famUy-wide studies, many of the subsections of the group and even individual genera were reviewed by, among others, Beecher (1953), Delacour (1943), Delacour and Edmond- Blanc (1934), Mainardi (1958), Stallcup (1954), Steiner (1955), and Woltei-s (1939, 1943, 1949, 1950, and 1957). All these studies yielded data wliich have been incorporated into the present study. Chapin (1932, pp. 380, 386-387) pointed out that the geograpliic dispersal of the different sections of the family may help reveal something of their past history and even of the relative time and place of their origmal deviation from the ancestral stock.