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Daily energy expenditure increases in response to low nutritional stress in an Arctic-breeding seabird with no effect on mortality

TitleDaily energy expenditure increases in response to low nutritional stress in an Arctic-breeding seabird with no effect on mortality
Publication TypeJournal Article
Year of Publication2009
AuthorsWelcker, J, Harding, AMA, Kitaysky, AS, Speakman, JR, Gabrielsen, GW
JournalFunctional Ecology
Volume23
Pagination1081–1090
Abstract

1. The regulation of energy expenditure in relation to food availability and its consequences forindividual fitness in free-ranging animals are poorly understood. Increased daily energy expenditure(DEE) may be viewed as the result of two different processes: expenditure may be forcedupwards by low food availability (forcing hypothesis) or enabled to increase by high levels offood resources (enabling hypothesis). Several studies have suggested long-term fitness costs dueto increased mortality as a trade-off to increased DEE.2. We examined the relationship between energy expenditure and an indirect measure of foodavailability, and the short-term fitness consequences associated with changes in DEE in a small,Arctic seabird, the little auk (Alle alle). We measured DEE of 43 parent little auks by the doublylabelled water method during two consecutive breeding seasons and inferred food availabilityfrom plasma concentrations of the stress hormone corticosterone (CORT).3. We found that DEE was elevated by 26Æ7% in the year with reduced levels of CORT, indicatingthat little auks responded to increased food availability by increasing their DEE. Theseresults support the enabling hypothesis. Elevated DEE was presumably caused by increasedparental effort as reflected by higher chick provisioning rates and larger chick meals, and wasassociated with fitness benefits in terms of enhanced current reproductive success.4. Contrary to earlier studies, our data did not indicate adverse effects associated with elevatedDEE; there was no negative relationship between DEE and the probability of adults returning tothe colony the following year. Instead, adult return rate was positively related to body mass,with lower return rates when food was limited.5. These results suggest that ecological consequences associated with limited resource availabilitymay outweigh possible direct negative physiological effects of elevated DEE.

DOI10.1111/j.1365-2435.2009.01585.x
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