SHULTZ, M. T.; KITAYSKY, A. S.; HOVNANIAN, C. N.; Univ. of Alaska Fairbanks; Univ. of Alaska Fairbanks; Univ. of Alaska Fairbanks: Functional role of corticosterone release during food shortages in Black-legged Kittiwakes

Seabirds respond to food shortages by increasing secretion of corticosterone (CORT). Elevated CORT secretion has been proposed as a mechanism allowing seabirds to maximize their fitness under varying foraging conditions. In this study we examined short and long-term consequences of a suppressed HPA-axis sensitivity to natural variations in food availability in kittiwakes rearing chicks in the eastern Bering Sea. We implanted birds subcutaneously with either exogenous CORT (experimental individuals) or placebo (controls) for a two-day period. We recorded nest attendance, the duration of foraging trips, chick feeding and begging behavior. We measured baseline CORT levels immediately prior to implantation and before implant removal two days later. We found that foraging conditions deteriorated during the two days of the experiment, as reflected in elevated chick begging and changed nest attendance by parents. Controls responded to this temporary food shortage by increasing CORT secretion, whereas baseline levels of CORT remained unchanged in experimental birds. Controls, but not experimental birds, responded to the increase in chick begging by feeding them more often. We also found that three weeks after implant removal, chicks and mates of CORT implanted birds had significantly higher acute stress-induced CORT levels than those from control nests. These results confirm a functional role of HPA-axis activation during food shortages � in chick-rearing kittiwakes, failure to respond to a food shortage by increasing CORT secretion results in a compromised physiological condition of mates and current offspring. The affects on residual fitness will also be discussed.