Corticosterone facilitates begging and affects resource allocation in the black-legged kittiwake

Parent black-legged kittiwakes (Rissa tridactyla) and their dependent chick s respond to food shortages by increasing circulating levels of corticoster one. To examine the behavioral significance of corticosterone release, we e xperimentally increased levels of circulating corticosterone in parents and chicks up to the levels observed during food shortages. We found that cort icosterone-implanted chicks begged more frequently than sham-implanted cont rols. Corticosterone-implanted chicks in broods of two begged more frequent ly than singletons. Parent kittiwakes then responded to the increase in cor ticosterone levels in their chicks by increasing chick-feeding rates. Howev er, feeding rates were not different among corticosterone-implanted chicks in broods of two and singletons. We also found that corticosterone-implante d parents spent more time away from the nest-perhaps foraging-and less time brooding/guarding chicks than sham-implanted controls. Untreated mates of the corticosterone-implanted bird did not compensate for the change in thei r partner's behavior; consequently, chicks were left unattended about 20% o f the time compared to 1% at the control nests. However, corticosterone-imp lanted parents did not decrease their chick-feeding rates. Our findings sug gest two functional implications of the increased corticosterone secretion during food shortages in the black-legged kittiwake: it facilitates begging in chicks, and it affects time allocated by parents to guarding young at t he nest. Thus, release of corticosterone might provide a mechanistic link b etween physiological condition and behavioral interactions among adults and their young.