Acoustic Basis for Individual Recognition by Voice in the Gannet

Abstract

A RECENT article by W. H. T.¹ reviewed the general question of the perceptual basis for group organization by birds and other vertebrates. It pointed out that successful social organization of colonially nesting sea birds must in many cases depend on a capacity for mutual recognition at some distance, at least between mates and oalso between parents and young, perhaps extending to other members of the group. While many species of birds (such as gulls and ducks) have visual powers so acute that they are able to recognize individuals at distances of 50 m or more, it was nevertheless shown that auditory recognition of individuals by subtle voice characteristics also plays a part—sometimes major—in identification. Indeed, in some examples of gulls, penguins, auks and terns, the evidence suggests that audiovocal recognition is likely to be more effective in the difficult conditions of life in a dense breeding colony than is visual recognition. As an example, work on the sandwich tern (Sterna sandvicensis)² has shown in some detail that the individual vocal patterns are constant and can be distinctively categorized in terms of a pattern of energy distribution expressed as frequency against time, which is so well shown by the spectrograph. This kind of pattern is, of course, what we ourselves hear as organized sounds with their characteristic temporal arrangement and tonal quality, as in speech or music.