The Perception of Pitch Constancy in Bird Songs
This chapter is concerned with how birds use pitch perception in song production and recognition. In contrast, the relationship between perception and production in songbirds is less widely appreciated. Song is a form of advertising, an acoustic billboard, used for territorial defense and mate acquisition by the oscine species. Songbirds must be able to recognize conspecific songs amidst a profusion of other sounds. Considerable research has focused on the song features important for species recognition. A second important function of song is its role in discrimination among individual conspecifics. Songbirds can distinguish territorial neighbors from strangers, singing, and approaching more to the songs of strangers than neighbors. The song elicits the expectation of a male conspecific. If songbirds use pitch interval as a feature in species recognition, then changing the frequency ratio in otherwise normal songs should reduce territorial response to playback.