P1.44 Wednesday, Jan. 4 Corticosterone, immune function, and behavior in free-living dark-eyed juncos HANAUER, RACHEL E.*; KETTERSON, ELLEN D.; Indiana University; Indiana University email@example.com
Pleiotropic effects of hormones can lead to integration of traits, potentially causing trade-offs that limit an organism’s adaptive responses to different environments. Previous studies in birds have found that the steroid hormone corticosterone affects multiple traits, including immune function and exploratory behavior, but it is unknown to what extent shared mediation by circulating corticosterone leads to correlation between these traits. If shared hormonal mediation leads to correlations between immune function and other hormone-mediated traits, then a mechanism exists for parasite selection on immune function to lead to changes in many other traits. I tested for correlations between corticosterone, constitutive immune function, and exploratory behavior in free-living dark-eyed juncos, Junco hyemalis. Baseline and elevated plasma corticosterone were assessed by taking blood samples from birds within three minutes of capture and again one hour later. Blood was also collected to measure bacteria-killing ability and hemagglutination. Exploratory boldness was assayed after holding the bird in captivity overnight. Infections by five types of parasites were also evaluated. These data will examine whether exploratory boldness and immune function covary, and if this covariation can be attributed to plasma corticosterone. By measuring the degree to which immune function is correlated with a hormone-mediated behavioral trait, these data will help address the plausibility of common hormonal mediation as a mechanism for the large-scale associations observed between parasite prevalence, life history, and behavior.