HABITUATION, RECOVERY AND THE SIMILARITY OF SONG TYPES WITHIN REPERTOIRES IN RED-WINGED BLACKBIRDS (AGELAIUS-PHOENICEUS) (AVES, EMBERIZIDAE)

Male red-winged blackbirds (Agelaius phoeniceus) respond to playback o f conspecific song on their territories with the song spread, a graded aggressive display in which males extend their wings to expose their red epaulets while singing. We show that the intensity of song spread display declines with repeated presentation of one song type, and reco vers when song types are switched. Recovery is greater for smirches be tween song types that are acoustically dissimilar than for switches be tween song types that are acoustically similar. Recovery is no differe nt for switches between two song types taken from the repertoires of d ifferent males than for switches between song types recorded from the same male. Analysis of acoustic features also indicates char song type s recorded from different males are nor more dissimilar than are song types from the same male. Our results do not support the idea that rep ertoires of red-winged blackbirds are composed of similar song types i n order to facilitate individual recognition. Rather, repertoires may be constructed of dissimilar song types, so as to help maintain the re sponse of listeners despite habituation.