Daily energy expenditure increases in response to low nutritional stress in an Arctic-breeding seabird with no effect on mortality
Article first published online: 4 JUN 2009
© 2009 The Authors. Journal compilation © 2009 British Ecological Society
Volume 23, Issue 6, pages 1081–1090, December 2009
How to Cite
Welcker, J., Harding, A. M. A., Kitaysky, A. S., Speakman, J. R. and Gabrielsen, G. W. (2009), Daily energy expenditure increases in response to low nutritional stress in an Arctic-breeding seabird with no effect on mortality. Functional Ecology, 23: 1081–1090. doi: 10.1111/j.1365-2435.2009.01585.x
- Issue published online: 9 NOV 2009
- Article first published online: 4 JUN 2009
- Received 15 January 2009; accepted 23 April 2009 Handling Editor: Sue Jackson
- body mass;
- doubly labelled water;
- little auk;
- parental effort;
1. The regulation of energy expenditure in relation to food availability and its consequences for individual 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 forced upwards by low food availability (forcing hypothesis) or enabled to increase by high levels of food resources (enabling hypothesis). Several studies have suggested long-term fitness costs due to increased mortality as a trade-off to increased DEE.
2. We examined the relationship between energy expenditure and an indirect measure of food availability, 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 doubly labelled water method during two consecutive breeding seasons and inferred food availability from plasma concentrations of the stress hormone corticosterone (CORT).
3. We found that DEE was elevated by 26·7% in the year with reduced levels of CORT, indicating that little auks responded to increased food availability by increasing their DEE. These results support the enabling hypothesis. Elevated DEE was presumably caused by increased parental effort as reflected by higher chick provisioning rates and larger chick meals, and was associated with fitness benefits in terms of enhanced current reproductive success.
4. Contrary to earlier studies, our data did not indicate adverse effects associated with elevated DEE; there was no negative relationship between DEE and the probability of adults returning to the 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 availability may outweigh possible direct negative physiological effects of elevated DEE.