Meeting Abstract
Seabirds live in variable environments where food availability is unpredictable and its abundance can fluctuate quickly. During food shortages, parents must balance tradeoffs between their current and future reproductive attempts by adjusting their chick provisioning behavior. Offspring hatching order and sex can influence the costs and benefits of parental investment. We tested the hypothesis that hatching hierarchy and chick sex affect parental provisioning in response to a sudden food reduction. Throughout the breeding season, we supplemented the diets of wild, nesting black-legged kittiwakes (Rissa tridactyla) daily. During early chick rearing, we withdrew the food supplementation from some (“withdraw”) nests but continued feeding control nests. We weighed chicks immediately before and 3 days after food withdrawal and weighed age-matched control chicks on the same dates. Blood samples were taken concurrent with weighings for quantification of plasma triglycerides, a lipid substrate indicative of avian nutritional state and change in body mass. The effects of food withdrawal primarily manifested themselves in first-hatched (A) chicks, with no significant differences between control and withdraw groups in second-hatched (B) chicks. Overall, withdraw A chicks gained less mass and showed decreases in triglyceride levels, resulting in significantly lower post-withdrawal body masses and plasma triglyceride concentrations compared to controls. Female A chicks exhibited the same pattern, but male A chicks did not. This variation in chick response may reflect either an increased vulnerability of female A chicks to food reduction or a parental decision to preferentially buffer male A chicks from the effects of food shortages.
