The biological significance of duetting and antiphonal song.

Duetting plays a very important part in the signal system between male and female in a large number of bird species, in particular species that inhabit tropical regions. These elaborate song patterns show many interesting features, of which only a few have been discussed here. Perhaps the most interesting result of our investigations of duetting is the light cast on the heretofore little appreciated precision and synthesizing power of avian aural perception, the great precision of response time and the equally great exactness of control of the vocal organs. The use of these vocal powers for individual recognition is in line with observations made over the past decade by B. Tschanz, C. G. Beer, myself and others. This work has shown that in many colonial nesting birds (for example auks, terns, gulls, gannets and penguins) brief calls of a half-second duration or less can have enough acoustic detail not only to serve as labels identifying the calling species but also to label the individual caller.