Antagonism of syringeal androgen receptors reduces the quality of female-preferred male song in canaries

Abstract

Adaptive performance of social behaviours requires the temporally precise activation of the relevant neural circuits based on the state of the environment. The actions of steroid hormones such as testosterone and its metabolites are critical in this activation for many social behaviours, especially those related to reproduction. Androgens, specifically androgenic action in the periphery, have been strongly implicated in regulating features of social behaviours that are considered to be especially important in mate attraction. Nevertheless, we currently have a relatively poor understanding of the different roles of steroid hormones in the regulation of social behaviour and its relevance to sexually selected traits. Here, we treat male canaries, Serinus canaria, with bicalutamide, an androgen receptor antagonist that does not cross the blood–brain barrier. Thus, we isolated androgen action to the periphery in order to target the syrinx, the avian vocal production organ. Bicalutamide treatment reduced song complexity but not song acoustic stereotypy. Bicalutamide-treated birds also showed reduced performance of ‘special trills’ and disrupted special syllable morphology. The performance and complexity of special trills in particular are able to stimulate copulation solicitation displays in female canaries to a substantially higher degree than any other component of canary song. These results highlight the nonredundant actions of steroid hormones in coordinating features of a complex behavioural pattern into an adaptive response, and suggest that androgen receptor expression in the relevant peripheral organs acts as a substrate on which sexual selection acts to amplify features of reproductive behaviours directly related to mate attraction.