Sexual Preferences of Female Brown-Headed Cowbirds (Molothrus Ater) for Perched Song Repertoires

Abstract

AbstractThe importance of repertoire size to mate choice by female songbirds has been widely debated but has not been addressed in Brown-headed Cowbirds (Molothrus ater; hereafter ”cowbirds”), despite extensive work on this species' songs. Male cowbirds cycle through repertoires of 2–8 perched song (PS) types in rapid sequences immediately prior to and during copulation, which suggests that repertoire size or content is important in mating contexts. Because male mating success in one well-studied cowbird population is correlated with large PS repertoires, we predicted that repertoire size is a cue in female mate choice. To test that prediction, we played three repetitions of conspecific songs in rapid succession to estradiol-primed female cowbirds (M. a. obscurus), to simulate the rapid song sequences that accompany naturally occurring matings. Females were presented with three different PS types, three repetitions of the same type, and heterospecific control songs of the same duration as the conspecific playbacks. Females gave longer copulation solicitation displays to three different PS types than to three repetitions of a single PS type, regardless of whether the playback songs were local or foreign. This is one of the few experimental studies on songbirds to show greater female responsiveness to a song repertoire presented so as to mimic singing in a natural mating context, and the first to present such a result for cowbirds. We conclude that presentation of multiple PS types is more sexually stimulating to females than a single type, because females prefer larger repertoires or singing patterns with a higher frequency of song-type switching.Preferencias Sexuales de Hembras de Molothrus ater por Repertorios de Canto de Percha