A Neuroethological Approach to Song Behavior and Perception in European Starlings: Interrelationships Among Testosterone, Neuroanatomy, Immediate Early Gene Expression, and Immune Function

Male European starlings produce a long complex song that is used by females to choose mates in a breeding context. Females tend to prefer males that produce songs organized into long bouts. The production of song is controlled by a specialized neural circuit called the song control system that is present in all oscine songbirds. Using long-bout song as a tool allowed us to explicate several aspects of the neural control of song perception and production in starlings. Variation in the volume of key song control nuclei, such as HVC and RA, correlates positively with variation in song bout length in adult starlings. IEG expression in the auditory forebrain of females is enhanced in response to long-bout song as compared to conspecific song organized into short bouts. Long-bout song as well as high rates of singing also predicts variation in measures of cellular and humoral immunity in male starlings. The cause and effect relationships among these variables still need to be elucidated. But T enhances the size of song control nuclei in starlings that correlate with the production of long-bout song preferred by females. Female choice therefore drives aspects of male physiology that results in long-bout song. In the female auditory forebrain, there is evidence for physiological responses to song as measured by IEG expression and electrophysiology that are tuned to aspects of male song that they prefer. However, these neural biases exhibit a plasticity that allows the females to modify their neural responses and memorize male songs as a function of the types of songs they encounter in their local social environment. These studies illustrate how behavioral investigations of functional significance can provide tools to implement a neuroethological investigation of behavioral mechanisms (see Fig. 9).