Meeting Abstract
One hypothesis for the function of vocal repertoires in songbirds is that singing multiple song types facilitates song type matching. Song type matching occurs when a male replies to the song of another male by singing the same song type. Song type matching has been hypothesized to have a number of social functions and was recently shown to be a reliable early threat signal in the song sparrow. To date, the majority of studies on song matching have focused on species with small to moderately sized repertoires (< 15 song types). Bachman’s sparrow repertoires range from 35-45 song types, and our field observations suggest that neighboring males perform song type matching during countersinging interactions. We tested the hypothesis that song type matching is an aggressive signal in Bachman’s sparrows through simulated territorial intrusions using a replica of a male Bachman’s sparrow coupled with playback of self-song types, ensuring the possibility of a full match. Subjects were played 9 of their own song types, each repeated 3 times. Each subject received two treatments: 1) songs were presented in random order (e.g, CEADB), and 2) songs were presented in the sequence in which the bird sang them during an undisturbed singing bout (ABCDE). During playbacks we took behavioral measures of aggressiveness and recorded all song responses. Subjects did not perform type-matches at above chance levels during either treatment, and we found no difference in aggressive response to the two treatments. Chance matching probabilities are low in a species with large repertoires, yet we commonly observe neighboring males match each other during bouts of countersinging. This suggests that song type matching functions in communication between established neighbors in this species, which predicts that playbacks of the songs of a neighboring male will elicit matching responses above chance level.
