Meeting Abstract
Breeding is an energetically expensive life history stage, particularly for short-lived organisms inhabiting highly variable environments. Corticosterone (cort), a glucocorticoid hormone, is released in response to noxious and unpredictable stimuli but also acts to increase metabolism at baseline levels. Successful individuals need to balance energy expenditure and costs to maximize fitness. However, evidence for a clear relationship between cort and fitness is lacking, complicated by the fact that this relationship can change within and between life-history stages. We collected repeated within-individual baseline and stress-induced plasma and feather cort levels using free-living mountain white-crowned sparrows (Zonotrichia leucophrys oriantha) from pre-breeding to post-breeding during variable environments. Additionally, we mapped territory size for breeding pairs using telemetry and collected data on reproductive success. Using nest cameras during incubation through fledging, we also measured reproductive effort. We discuss the link between the cort phenotype, territory size, and reproduction. These repeated measures data add to the growing research on understanding how flexible cort phenotypes act in changing environments.
