My research involves the integration between mechanism and function in animal behavior, with an emphasis on acoustic communication in birds and frogs. The principal current focus is on the song control system in the brains of songbirds. I emphasize a comparative, evolutionary approach to this system, and combine behavioral studies in the field with laboratory techniques in neuroendocrinology, neuroanatomy, molecular biology, and signal analysis. I am currently pursuing three major topics of study in the song system. One concerns the physiological and molecular mechanisms, and the behavioral consequences, of seasonal plasticity observed in the morphology of song regions of the brain. A second topic concerns the recruitment of new neurons to a song nucleus in the forebrain of adult birds, studied from the perspective of its physiological regulation and the influence of environmental factors. The third topic relates to the observation that neurons in song control nuclei receive input from auditory regions, and respond selectively to the presentation of conspecific song. I am investigating the role of song nuclei in the behavioral recognition of conspecific song in the contexts of mate choice and territorial defense.