Effects of season, water and predation risk on patch use by birds on the African savannah
Författare
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.
Avdelning/ar
Publiceringsår
2010
Språk
Engelska
Sidor
637-645
Publikation/Tidskrift/Serie
Oecologia
Volym
164
Issue
3
Dokumenttyp
Artikel i tidskrift
Förlag
Springer
Ämne
- Biological Sciences
- Ecology
Nyckelord
- Seasonal variation
- Dry tropics
- Giving-up density
- Water
- Foraging
- behavior
Status
Published
Forskningsgrupp
- Biodiversity and Conservation Science
- Life History and Functional Ecology
ISBN/ISSN/Övrigt
- ISSN: 1432-1939