Abstract
Male European starlings (Sturnus vulgaris) sing throughout the year, but the social factors that motivate singing behavior differ depending upon the context in which song is produced. In a non-breeding context (when testosterone concentrations are low), starlings form large, mixed-sex flocks and song is involved in flock cohesion and perhaps maintenance of social hierarchies. In contrast, in a breeding context (when testosterone concentrations are high), male song plays a direct role in mate attraction. How the nervous system ensures that song production occurs in an appropriate context in response to appropriate stimuli is not well understood. The song control system regulates song production, learning, and, to some extent, perception; however, these nuclei do not appear to regulate the social context in which song is produced. A network of steroid hormone sensitive nuclei of the basal forebrain and midbrain regulates social behavior. The present study used the immediate early gene cFOS to explore possible involvement of these regions in context-dependent song production. Numbers of cFOS-labeled cells in the medial bed nucleus of the stria terminalis, anterior hypothalamus, and ventromedial nucleus of the hypothalamus related positively only to song produced in a breeding context. In contrast, numbers of cFOS-labeled cells in three zones of the lateral septum related positively only to song produced in a non-breeding context. Taken together, these data suggest differential regulation of male starling song by social behavior nuclei depending upon the breeding context in which it is produced.