Meeting Abstract
Female mating decisions are influenced by the quality of male courtship displays. In many species, males produce vocal signals that are designed to attract females; however not all females are attracted by these signals. One possibility is that environmental factors alter neural mechanisms underlying reward and motivation so that male courtship is attractive when conditions are most favorable for an individual to breed. I will present studies exploring this hypothesis in female European starlings Sturnus vulgaris. In starlings the availability of a nest site is critical for breeding. In the breeding season, females housed in aviaries with nest boxes approach males, sing, and displace other females more than females in aviaries without nest sites. They also tend to have higher estradiol concentrations than females without boxes. These differences occur even in females that do not enter and defend an available box. In contrast, the affective state induced by hearing male courtship song depends on whether a female is actively defending a nest site. Using a classic conditioned place preference test of reward we found that hearing male song induced reward in females that defended nest boxes but not in females that did not. These differences were accompanied by differences in dopamine- and opioid-related genes and proteins in the medial preoptic nucleus, ventromedial hypothalamus, and nucleus accumbens. This suggests that the mere presence of a nest site initiates breeding-related changes in physiology and behavior, but possession of a nest site induces additional neural changes to increase the reward value of male courtship song. Overall, these findings suggest that environmental factors alter motivation and reward neural systems to fine-tune female responses to male courtship song to maximize breeding success.
