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 own largely unpublished observational data: J. P. Chapin, N. E. 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. 



