Resource allocation in breeding seabirds: responses to fluctuations in their food supply

摘要: In the vicinity of Pribilof Islands in Bering Sea, abundance food available to surface-foraging seabirds was greater during chick-rearing period 1988 than 1987, whereas pursuit-diving 1987. Here we examine how breeding success and resource allocation black-legged kittiwakes Rissa tridactyla (BLKI) thick-billed murres Uria lomvia (TBMU) varied with fluctuations their supply. We also a difference among parents raising chicks at large colony on St. George Island those nearby small Paul Island. studied (BS), field metabolic rates (FMR, assessed by using doubly labeled water), foraging distribution, nest attendance growth rate (GR) chicks. The BS BLKIs lower 1987 (a season less abundant for kittiwakes) more food), had higher FMRs 1988. At-sea distributions suggested that foraged farther from colonies, which could have resulted FMR parents. GR BLKI did not vary between TBMUs significantly different TBMUs) food). Parent similar seasons. Densities were within 20 km around colonies Although total time parent spent inter-seasonally, they performed trips shorter duration 1988, TBMU Inter-colony comparisons do suggest reproducing work harder raise young compared colony. failed colony, one-third fledged however, RS colonies. Also, both Furthermore, years feeding These results supply affect seabirds. However, decrease is likely cause an increase energy expenditures BLKIs, are affected. For TBMUs, shortages chicks, but