Meeting Abstract
Breeding is considered one of the highest energetically challenging stages within the annual cycle. Environmental disturbances during the breeding season can influence an individual’s decision to breed or continue with an initiated breeding attempt. The general reproductive effort model attempts to predict the resources that will be allocated to a current reproductive bout or to future survival by aborting the current reproductive attempt. Life history theory predicts that short lived species should devote more resources towards a reproductive event because brood value is far greater than compared to that of long lived species that have multiple opportunities to breed. Previous bird studies have used endocrine correlates to understand the regulation of parental investment in response to stress. The two hormones investigated have been prolactin, which promotes parental investment, and corticosterone which promotes nest abandonment. Work in long lived sea birds has shown that prolactin levels decrease in response to a stressor but the magnitude of the decline was positively correlated with future reproductive potential. Here we present corticosterone and prolactin data collected following a standardized stressor, acute restraint handling, from a short lived arctic breeding, migratory songbird the white-crowned sparrow (Zonotrichia leucophrys gambelii) at multiple stages of the breeding and non-breeding seasons. These data show that both prolactin and corticosterone are modulated seasonally. Prolactin levels do not change in response to a standardized stressor which may be a physiological mechanism for maximizing parental investment in a harsh environment with a short breeding season.
