The Condor

There is probably more ignorance concerning pair-formation than there is of any other aspect of bird behavior. This paper attempts to summarize existing knowledge on this subject in order to stimulate further work. I am greatly indebted to Dr. Ernst Mayr and Dr. G. Kingsley Noble for their stimulating discussions with me, and to Dr. Alden H. Miller for seeing the paper through the press, an undertaking which was rendered necessary by the international situation. A review such as the present one involves a large number of references. Papers contributing to the general discussion are cited in the standard way, but if those dealing primarily with a particular species were treated in the same manner, the text would be heavily encumbered with authors’ names and years of publication. Hence papers of the latter type are listed at the end of the paper (p. 284) under the species concerned and are not referred to elsewhere. While this means a little extra trouble for the reader, it saves considerable space. Further, where one recent paper summarizes previous work on a species, I have usually thought it unnecessary to give the earlier references as well. The references are not a complete bibliography of bird courtship; only papers dealing explicitly with pair-formation are included, and in this field I have omitted many articles on typically territorial species of passerine birds, as these are now too well known to need detailed reference, In such a wide field, some references to pair-formation have almost certainly been overlooked, but in other instances omission has been deliberate where, as with the Ostrich (Strutk~o camelus), Great Bustard (Otis tar&) and others, the descriptions are too vague to be of value.