A distinct reed bunting dawn song and its relation to extrapair paternity

Abstract

Elaborate birdsong is thought to have evolved under sexual selection. Extrapair mating can enforce sexual selection and thus the selection of song traits. We investigated song rate and song diversity, two song traits previously shown to be under sexual selection, in relation to paternity success in the reed bunting, Emberiza schoeniclus, a species with high levels of extrapair paternity. We focused our investigations on songs sung during the dawn chorus because singing at dawn is likely to be an honest signal and there is increasing evidence that females engage in extrapair copulations early in the morning. We classified a previously denoted continuous song, which is mainly sung during the dawn chorus, as a new song type in this species. Males with high song rate and high song diversity were more likely to gain extrapair paternity. These two song traits were also positively related to the number of extrapair offspring sired. However, most of the variance in extrapair paternity success was explained by age. Old males sired significantly more extrapair young than young males. Possibly, the new song type plays an important role in the female choice of extrapair mates. Reed bunting females may prefer males that sing at high rates and with high diversity because this indicates high phenotypic and genetic quality. Alternatively, these song parameters may be linked to other sexually selected traits or be important in the intersexual competition for extrapair fertilizations.