Meeting Abstract

P1.77  Thursday, Jan. 3  Stress in prothonotary warblers (Protonotaria citrea) in response to breeding stage and food availability MOORE, J.R.*; WALTERS, J.R.; MOORE, I.T.; Virginia Tech; Virginia Tech; Virginia Tech s2jrmoor@vt.edu

The physiological stress response of free-living vertebrates to unpredictable events, such as storms, has been a recent focus in field endocrinology. However, how vertebrates hormonally respond to challenging events that are predictable, such as successfully rearing young, and how stress hormones may be influenced by the unpredictability of food availability are not well understood. Previous studies have found that experimental increases in food abundance can lead to a decrease in both baseline and maximal glucocorticoids and an increase in egg production. We wanted to look at the effect of food abundance on plasma glucocorticoids across different breeding stages as well as reproductive success in a migratory bird. To assess the effects of breeding stage on the stress response, baseline and maximal glucocorticoid levels were measured in female prothonotary warblers (PROW) at four different sites in the James River Virginia watershed. Hormone levels were collected during the incubation and nestling stages of PROW breeding cycle. Reproductive success was measured as the number of assumed fledglings per clutch. Estimates of arthropod abundances, the PROWs primary food source, were also measured over the course of the breeding season using frass collecting nets to examine variation in the stress response of female PROW in relation to relative food availability. From initial analyses, there appear to be no differences in reproductive success between sites. We predict an increase in both baseline and maximal glucocorticoid levels from the incubation stage to the nestling stage. Further, we predict an increase in baseline and maximum glucocorticoid levels associated with low food availability.