
Meeting Abstract
P2.161 Monday, Jan. 5 Increased territorial responses in urban populations of two Sonoran Desert birds: Hormones or Ecology? FOKIDIS, H. Bobby*; ORCHINIK, Miles; DEVICHE, Pierre; Arizona State University; Arizona State University; Arizona State University bfokidis@asu.edu
In many birds, the onset of breeding is marked by territory establishment and its subsequent defense from conspecific intrusion. Territories may be defended for various reasons including the monopolization of spatially limited resources. These resources can vary between habitats, which in turn may influence territorial behavior. We measured the territorial behavior of male Curve-billed Thrashers, Toxostoma curvirostre, and Aberts Towhees, Pipilo aberti, belonging to urban and rural Arizona populations through direct observation of birds in response to conspecific song playback recordings. Corticosterone (CORT) has been associated with avoidance behavior in some species. In circulation, most CORT in birds is reversibly bound to corticosterone binding globulin (CBG) and this interaction presumably mediates the amount of free (unbound) hormone available to interact with cellular receptors. We measured total and estimated free plasma CORT concentrations in urban and desert thrashers and towhees and correlated these concentrations to behavioral responses to song playback. We also measured population densities of the two species in urban and rural areas as it may influence aggressive interactions between conspecifics. Both urban thrashers and towhees were significantly more aggressive than desert conspecifics but this difference was not related to total or free plasma CORT or to differences in population density between habitats. These results will be discussed in the context of the effects of urbanization on behavior and endocrine physiology.