Vocal Mimicry and Interspecific Aggression in Songbirds: Experiments Using White-Crowned Sparrow Imitation of Song Sparrow Song

A series of playback experiments was carried out to determine whether territorial male song sparrows could discriminate between their own species song, and the same song produced by a white-crowned sparrow. In two out of three measures of response, the males did not discriminate between model and mimic song. In constrast, most males showed no response to control white-crowned sparrow song, although two individuals showed a strong interspecific response. Other examples of interspecific aggression were also detected during the experiments. The results are discussed in relation to recent studies on interspecific song learning and the competition hypothesis of vocal mimicry in songbirds.