BENOWITZ-FREDERICKS, Morgan; KITAYSKY, Alexander S.; HATCH, Scott A.; Univ. Alaska, Fairbanks; Univ. Washington, Seattle; Univ. Alaska, Fairbanks; U.S. Geological Survey, Alaska Science Center : Yolk androgens in Black-legged kittiwakes: Consequences of food supplementation

Black-legged kittiwakes are seabirds that frequently face food shortages during reproduction. Siblicide resulting in loss of the beta chick reduces competition among nest mates for limited food resources. Several studies have suggested that avian brood reduction may be mediated by maternal effects � specifically via deposition of androgens in the yolk. In this study, we experimentally altered food availability by providing free-living kittiwakes with access to unlimited food 3 times per day, and assessed consequences on steroid deposition in yolk of alpha and beta eggs in 2-egg clutches. We found that testosterone and androstenedione were always higher in beta than in alpha eggs. However, beta eggs from unsupplemented nests had higher testosterone than beta eggs from supplemented nests. We conclude that black-legged kittiwakes deposit androgens in egg yolk in a condition-dependent manner, and that elevated androgens in beta eggs may have the capacity to facilitate rather than inhibit brood reduction depending on food availability.