SONG PERCEPTION IN THE SONG SPARROW - BIRDS CLASSIFY BY SONG TYPE BUT NOT BY SINGER

Recent theories have identified song repertoires and song sharing among neighbours as potential obstacles to individual recognition. These obstacles can be at least partially overcome if the differing song types of an individual have common 'voice' or 'signature' traits, for these would allow a listener to discriminate between different singers' renditions of the same song type and generalize between the different song types of the same singer. Two perceptual experiments were carried out in the laboratory using operant conditioning methods, to compare the relative effects of song sharing and vocal signature traits on song discrimination. Song sparrows were first trained to classify the songs of several singers and then tested on unfamiliar song types of the same singers and unfamiliar shared songs of neighbours of the singers. Subjects failed to generalize from the familiar to unfamiliar song types of a singer, suggesting that 'voice' traits in song sparrows are non-existent or trivial at best. Subjects did, on the other hand, confuse the shared song types of different singers. These findings suggest that learning to discriminate between the shared song types of neighbours in the field may be no simple task, and that the songs of newcomers might be confused with those of residents, at least for a time. © 1993 The Association for the Study of Animal Behaviour.