Meeting Abstract
P1.75 Thursday, Jan. 3 Adrenocortical responsiveness to capture and restraint in the eastern bluebird (Sialia sialis): effects of repeated handling LYNN, S.E.*; PRINCE, L.E.; The College of Wooster; The College of Wooster slynn@wooster.edu
When faced with unpredictable conditions, most birds activate the hypothalamo-pituitary-adrenal (HPA) axis, resulting in enhanced secretion of corticosterone (CORT). A standardized capture/restraint paradigm has been widely used to compare HPA responsiveness among individuals, populations, and species. A key assumption of this paradigm is that restraint represents a novel stressor; however, previous studies have shown that prior experience with the capture/restraint protocol itself may alter HPA sensitivity in captive birds. To our knowledge, no such studies have been conducted in free-living birds. We sought (1) to characterize the CORT response to restraint in breeding eastern bluebirds, and (2) to determine if habituation to restraint could occur in birds sampled in two subsequent broods. We captured adults during the nestling phase of the first and/or second brood of the season, and collected serial blood samples over an hour of restraint to be analyzed for CORT and corticosteroid binding globulin. All birds responded with elevated CORT, but we found no sex-specific differences in CORT secretion. We also found no difference in CORT dynamics between females captured, restrained, and bled for the first time during the first brood or the second brood. Thus, HPA activity in response to a novel stressor remained unchanged as the breeding season progressed. However, for a subset of females captured and bled twice during a single breeding season, integrated total and free CORT levels were lower during the second capture/restraint bout than the first. Thus, as little as one prior experience with the capture/restraint protocol was sufficient to alter HPA responsiveness in free-living birds. Our data confirm that caution should be exercised in drawing conclusions regarding HPA responses when birds are repeatedly sampled.
