Present address: Community and Conservation Ecology Group (COCON), Center for Ecological and Evolutionary Studies, University of Groningen, PO Box 14, 9750AA Haren, The Netherlands
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Site selection and resource depletion in black-tailed godwits Limosa l. limosa eating rice during northward migration
Article first published online: 8 JAN 2010
DOI: 10.1111/j.1365-2656.2009.01654.x
© 2010 The Authors. Journal compilation © 2010 British Ecological Society
Additional Information
How to Cite
Lourenço, P. M., Mandema, F. S., Hooijmeijer, J. C., Granadeiro, J. P. and Piersma, T. (2010), Site selection and resource depletion in black-tailed godwits Limosa l. limosa eating rice during northward migration. Journal of Animal Ecology, 79: 522–528. doi: 10.1111/j.1365-2656.2009.01654.x
Publication History
- Issue published online: 22 MAR 2010
- Article first published online: 8 JAN 2010
- Received 28 February 2009; accepted 14 December 2009 Handling Editor: Stuart Bearhop
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Keywords:
- foraging decisions;
- functional response;
- habitat selection;
- individual movements;
- intake rate;
- rice fields;
- stopover ecology
Summary
1. During migratory stopovers, animals are under strong time stress and need to maximize intake rates. We examine how foragers react to resource depletion by studying the foraging ecology and foraging site selection of black-tailed godwits Limosa l. limosa staging in rice fields during their northward migration stopover (January–March 2007).
2. We analysed godwit abundance and foraging behaviour, sampled the availability of rice in the fields and used the functional response model to predict the giving-up density (GUD) of rice kernels when godwits should give up a rice field. Sightings of individually colour-marked birds were used to verify whether individuals moving between rice fields confirmed the predicted GUD.
3. Black-tailed godwit intake rates at different rice densities fitted Holling’s functional response curve. The predicted GUD of rice necessary to balance allometric estimates of daily energy expenditure (DEE) and measured time budgets were confirmed by GUD measured in the field.
4. Individually marked birds moved towards rice fields with higher rather than lower rice densities more often than randomly expected. These birds increased the measured intake rates after this move.
5. Godwit foraging caused a decrease in the rice density of individual fields during the stopover period. Despite this, overall intake rates remained constant as godwits reacted to resource depletion by moving to a new foraging site as soon as their intake rate falls below the required levels to achieve DEE.