Effects of season, water and predation risk on patch use by birds on the African savannah
Author
Summary, in English
Birds from semi-arid regions may suffer dehydration during hot, dry seasons with low food availability. During this period, both energetic costs and water requirements for thermoregulation increase, limiting the scope of activity. For granivorous birds feeding on dry seeds, this is a major challenge and availability of water may affect the value of food. Water availability could (1) increase the value of a food patch when the surrounding environment is poor, due to an increase in the marginal value of energy, and (2) increase the value of the entire environment to the forager when environmental quality increases, due to an increase in the marginal value of time. We aimed to test this by measuring giving-up densities (GUDs, remaining food densities after foraging) of granivorous birds in the presence or absence of filled water pots, at different seasons differing in background food and water availability. We predicted that GUDs will increase with water provision during the dry season with moderate food, but in the early wet season with low food and water availability, GUDs will decrease with water provision. Later in the wet season, our experimental addition of water should have no effect. During seasons with low water availability but differing in food availability, results confirmed our predictions. However, when water became more abundant as the wet season progressed, birds still foraged more intensely during days with added water. In all seasons, birds fed more intensely in cover than in exposed areas, suggesting that predation risk rather than heat influenced microhabitat selection.
Department/s
Publishing year
2010
Language
English
Pages
637-645
Publication/Series
Oecologia
Volume
164
Issue
3
Document type
Journal article
Publisher
Springer
Topic
- Biological Sciences
- Ecology
Keywords
- Seasonal variation
- Dry tropics
- Giving-up density
- Water
- Foraging
- behavior
Status
Published
Research group
- Biodiversity and Conservation Science
- Life History and Functional Ecology
ISBN/ISSN/Other
- ISSN: 1432-1939