Behavioral Sex Differences and Hormonal Control in a Bird with an Elaborate Courtship Display.

Gonadal hormones can activate performance of reproductive behavior in adult animals, but also organize sex-specific neural circuits developmentally. Few studies have examined the hormonal basis of sex differences in the performance of elaborate, physically complex, and energetic male courtship displays. Here we describe our studies over more than 20 years examining sex difference and hormonal control of courtship in Golden-collared manakins (Manacus vitellinus) of Panamanian rainforests. Our recent studies of birds studied in an artificial "lek" in a rainforest aviary provide many new insights. Wild and captive males and females differ markedly in their performance of male-typical behaviors. Testosterone (T) treatment augments performance of virtually all of these behaviors in juvenile males with low levels of circulating T. By contrast, T-treatment of females (with low circulating T) either failed to activate some behaviors or activated male behaviors weakly or strongly. These results are discussed within a framework of our appreciation for hormonal versus genetic basis for sex differences in behavior with speculation about the neural mechanisms producing these patterns of hormonal activation.