SONG LEARNING, EARLY NUTRITION AND SEXUAL SELECTION IN SONGBIRDS

The developmental processes through which songbirds acquire their spec ies-typical songs have been well-studied from a proximate perspective, but less attention has been given to the ultimate question of why bir ds learn to sing. We present a new hypothesis for the adaptive signifi cance of song learning in songbirds, suggesting that this specialized form of vocal development provides an indicator mechanism by which fem ales can accurately assess the quality of potential mates. This hypoth esis expands on the established idea that song earn provide an indicat or of male quality, but it explicitly links the variation in song expr ession that females use to choose mates to the developmental processes through which song is acquired. How well a male sings-reflected in re pertoire size or in other learned features of a male's singing behavio r-provides an honest indicator of quality because the timing of song l earning and, more importantly, the timing of the development of brain structures mediating learning corresponds to a period in development d uring which young songbirds are most likely to undergo nutritional str ess. This correspondence means that song learning can provide a sensit ive indicator of early developmental history in general, which in turn reflects various aspects of the phenotypic and genotypic quality of a potential mate.