Meeting Abstract

P2.183  Thursday, Jan. 5  Repeatability and Plasticity of Baseline Corticosterone MADLIGER, C.L.*; LOVE, O.P.; University of Windsor, Ontario; University of Windsor, Ontario madlige@uwindsor.ca

Evolutionary physiologists have recently begun to appreciate the adaptive significance of variation in baseline glucocorticoid levels, and its potential for mediating life history decisions related to energetic condition and environmental quality. To determine whether, and if so how, selection can act on glucocorticoid concentrations, we must determine the consistency (i.e., the repeatability) of such hormone levels. Studies presenting repeatability estimates of baseline corticosterone (CORT) concentrations in wild populations have reported variable results, and few have investigated repeatability within any environmental context. Here we present data on the repeatability and plasticity of baseline CORT in Tree Swallows (Tachycineta bicolor) within and across breeding seasons, with specific consideration of the contexts of age, reproductive stage, and habitat quality. These results can help determine whether static measures of baseline glucocorticoids, or plasticity in such traits, are more important for predicting fitness.