Breeding context-dependent neural regulation of singing behavior in male European starlings (Sturnus vulgaris)

Vocal communication among conspecifics can occur in a variety of contexts. Often, much can be inferred about the meaning of a vocal signal by considering the social and physiological condition of both the signaler and receiver. An intriguing possibility is that the proximate mechanisms that regulate vocal behavior differ depending upon the context in which it occurs. This possibility is the unifying element of my dissertation research. Songbirds provide a powerful model for asking questions about how the social environment, hormones, and the brain interact to regulate vocal communication. The focus of my dissertation is to explore this interaction and ask whether reproductive context influences the way the nervous system regulates singing behavior in male European starling (Sturnus vulgaris).;Using immediate early genes (IEGs) as indirect markers of neuronal activity, the first chapter demonstrates that activity in song control and social behavior brain regions correlates with singing behavior context-dependently. The second and third chapters investigate the role of the neurotransmitter dopamine (DA) in the context-dependent neural regulation of male starling song. In chapter two, immunocytochemistry for tyrosine hydroxylase (TH, the rate-limiting enzyme in DA synthesis) and dopamine beta hydroxylase (DBH, the enzyme that converts DA into norepinephrine) is used to investigate the relationship between DA synthesis and breeding versus non-breeding context singing behavior. These studies suggest that DA synthesis in song control/social behavior brain regions only correlates with breeding context song. Chapter three uses DA receptor autoradiography to explore the relationship between D1 and D2 receptor density and breeding versus non-breeding context singing behavior. Correlation analysis reveals D1 receptor density in social behavior brain areas is most tightly linked with breeding context song. In two social behavior regions, however, D1 receptor density also correlates with non-breeding context song. Together, these patterns suggest context-dependent differences in the dynamics of DA release and/or D1 receptor kinetics associated with singing behavior. Together, these studies demonstrate differences in how the starling brain regulates breeding and non-breeding context song and highlight DA as a context-dependent modulator of communication in songbirds.