The goal of this project is to understand the hormonal basis of social behavior, particularly aggressive and parental behavior in birds. The research will focus on two closely related species of jays that live in close proximity to each other in Arizona but have very different social systems. This collaborative research effort will bring together Dr. Jerram Brown's long-term (more than 20-year) study of Mexican jays, in which the genealogies and breeding history of a large number of color-banded birds are known, with a study by Dr. Carol Vleck on the hormonal basis for the different behaviors that individual jays exhibit. Of particular interest are (1) the mechanisms that permit co-existence of many individuals within a social group in Mexican jays but not in scrub jays and (2) the mechanisms that promote parental-like (helping) behavior in non-breeding Mexican jays (e.g., why these birds help raise the young of others rather than breeding themselves). The research will concentrate on testosterone, which in other species is important in controlling both aggressive and sexual interactions between individuals, and on prolactin, which is important in promoting parental behavior in birds. By correlating hormone levels in small blood samples with the behavior of the birds, and by altering the levels of these hormones in free-living individuals, Drs. Vleck and Brown will test the hypotheses that (1) high levels of prolactin are responsible for both parental and helping behavior and that (2) group living is promoted by a general decrease in testosterone levels. This study will shed light on the hormonal basis for the differences in reproductive behaviors of individuals within one species and will also provide information on the hormonal bases of very diverse social organizations in different species.
