Both females and males of many animals possess elaborate displays, such as solo songs and duets of songbirds. We know little about the function of female song or what selects for duets. To examine their possible functions, we played female solos, duets and a heterospecific control to pairs of troupials (Icterus icterus). Both sexes responded strongly to duets by approaching the playback speaker significantly closer, faster, and more often compared to female solos or the control. Neither sex responded strongly to female solos; troupials approached closer, sang sooner, and duetted more following female solos than the control, but this difference was not significant. Our results indicate that troupial duets pose a greater threat than female solos and female troupial solos are not particularly threatening. Troupial duets may be especially threatening because they indicate the presence of a mated pair, which likely poses a greater territorial threat than lone, unmated birds.
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