BREWER, J.H.**; O’REILLY, K.M.; BUCK, C.L.; Univ. of Alaska Fairbanks; Univ. of Portland; Univ. of Alaska Fairbanks: Interannual variation in adrenal responsiveness of black-legged kittiwake chicks: An indicator of forage availability?

Productivity (fledglings/nest attempt) of black-legged kittiwakes (Rissa tridactyla) is strongly influenced by local foraging conditions. Recent studies demonstrate that corticosterone levels of breeding kittiwakes correlate inversely with both productivity and forage availability. Increased plasma concentration of corticosterone in kittiwake chicks is known to promote begging behavior and facilitate increased metabolism of lean tissue; however, the relationship between adrenal responsiveness of chicks and foraging conditions experienced by their parents has not been previously explored. We set out to test the hypothesis that adrenal responsiveness of kittiwake chicks is sensitive to local forage availability as reflected by productivity. In 2002-2005, we monitored productivity at 21 colonies in Chiniak Bay, Alaska and sampled chicks for blood at <3, 10, 30, and 50 minutes post-capture. Corticosterone concentrations were subsequently determined by radioimmunoassay. Productivity was greatest in 2002, then progressively decreased in 2003 and 2004 before improving slightly in 2005. Baseline levels (<3 minutes post-capture) of corticosterone did not significantly differ among years; however, adrenal responsiveness was inversely related to productivity. Chicks in low productivity years exhibited both a greater and more protracted increase in plasma corticosterone levels, features indicative of chronic stress. These results suggest that corticosterone concentration in black-legged kittiwake chicks may be a reliable indicator of foraging conditions experienced by their parents.