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Effects of season, water and predation risk on patch use by birds on the African savannah

Molokwu, Mary LU ; Nilsson, Jan-Åke LU ; Ottosson, Ulf LU and Olsson, Ola LU (2010) In Oecologia 164(3). p.637-645
Abstract
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Seasonal variation, Dry tropics, Giving-up density, Water, Foraging, behavior
in
Oecologia
volume
164
issue
3
pages
637 - 645
publisher
Springer
external identifiers
  • wos:000283097900006
  • scopus:77958015910
ISSN
1432-1939
DOI
10.1007/s00442-010-1781-3
project
BECC
language
English
LU publication?
yes
id
3330e71b-2fbd-4a7a-bebc-3b92b82ccd9f (old id 1720651)
date added to LUP
2010-12-09 12:47:42
date last changed
2018-05-29 10:21:37
@article{3330e71b-2fbd-4a7a-bebc-3b92b82ccd9f,
  abstract     = {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.},
  author       = {Molokwu, Mary and Nilsson, Jan-Åke and Ottosson, Ulf and Olsson, Ola},
  issn         = {1432-1939},
  keyword      = {Seasonal variation,Dry tropics,Giving-up density,Water,Foraging,behavior},
  language     = {eng},
  number       = {3},
  pages        = {637--645},
  publisher    = {Springer},
  series       = {Oecologia},
  title        = {Effects of season, water and predation risk on patch use by birds on the African savannah},
  url          = {http://dx.doi.org/10.1007/s00442-010-1781-3},
  volume       = {164},
  year         = {2010},
}