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Diet selection in birds: trade-off between energetic content and digestibility of seeds

Molokwu, Mary LU ; Nilsson, Jan-Åke LU and Olsson, Ola LU (2011) In Behavioral Ecology 22(3). p.639-647
Abstract
Partial preferences may occur due to differences in profitability and encounter probability between food types within a patch. In the expanding specialist diet strategy, a forager goes from being partially selective on the preferred, most profitable food, to being opportunistic, after the preferred food has been depleted to a certain critical level. We studied the diet selection strategies of birds foraging on 2 seed types-crushed peanut Arachis hypogaea and husked millet Pennisetum gambiense, in a woodland savannah near Jos, Nigeria. Peanut contains more fat and energy, whereas millet is richer in carbohydrates. We tested 2 hypotheses: 1) energy content will determine seed preference for seeds with relatively similar handling times and 2)... (More)
Partial preferences may occur due to differences in profitability and encounter probability between food types within a patch. In the expanding specialist diet strategy, a forager goes from being partially selective on the preferred, most profitable food, to being opportunistic, after the preferred food has been depleted to a certain critical level. We studied the diet selection strategies of birds foraging on 2 seed types-crushed peanut Arachis hypogaea and husked millet Pennisetum gambiense, in a woodland savannah near Jos, Nigeria. Peanut contains more fat and energy, whereas millet is richer in carbohydrates. We tested 2 hypotheses: 1) energy content will determine seed preference for seeds with relatively similar handling times and 2) diet selection will vary seasonally in response to nutritional demands. We carried out 2 experiments, one with both seed types occurring in a single patch and another with both occurring in 2 separate patches during different seasons. The diet selection strategy of the birds was similar to the expanding specialist. Initially, peanuts seemed to be the preferred food, probably due to their high profitability, but overall millet was preferred. However, the expansion point was not determined by the amount of peanut seeds left, as predicted, but rather by the amount eaten. We propose that a trade-off is created by the fact that peanut has higher energy density but at the same time contains secondary compounds. Selectivity for millet decreased slightly in the wet season when more peanuts were taken possibly due to increasing nutritional demands during breeding. Key words: diet model, diet selection, dry tropics, energy, expanding specialist, foraging behavior, granivorous birds, savannah, seasonality, secondary compounds, seed preference, water. [Behav Ecol 22: 639-647 (2011)] (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Behavioral Ecology
volume
22
issue
3
pages
639 - 647
publisher
Oxford University Press
external identifiers
  • wos:000289839600028
  • scopus:79955416251
ISSN
1045-2249
DOI
10.1093/beheco/arr025
language
English
LU publication?
yes
id
1127ea13-51a9-45cb-be09-c767cd8885fe (old id 1964669)
date added to LUP
2011-05-23 14:38:12
date last changed
2017-09-17 05:44:12
@article{1127ea13-51a9-45cb-be09-c767cd8885fe,
  abstract     = {Partial preferences may occur due to differences in profitability and encounter probability between food types within a patch. In the expanding specialist diet strategy, a forager goes from being partially selective on the preferred, most profitable food, to being opportunistic, after the preferred food has been depleted to a certain critical level. We studied the diet selection strategies of birds foraging on 2 seed types-crushed peanut Arachis hypogaea and husked millet Pennisetum gambiense, in a woodland savannah near Jos, Nigeria. Peanut contains more fat and energy, whereas millet is richer in carbohydrates. We tested 2 hypotheses: 1) energy content will determine seed preference for seeds with relatively similar handling times and 2) diet selection will vary seasonally in response to nutritional demands. We carried out 2 experiments, one with both seed types occurring in a single patch and another with both occurring in 2 separate patches during different seasons. The diet selection strategy of the birds was similar to the expanding specialist. Initially, peanuts seemed to be the preferred food, probably due to their high profitability, but overall millet was preferred. However, the expansion point was not determined by the amount of peanut seeds left, as predicted, but rather by the amount eaten. We propose that a trade-off is created by the fact that peanut has higher energy density but at the same time contains secondary compounds. Selectivity for millet decreased slightly in the wet season when more peanuts were taken possibly due to increasing nutritional demands during breeding. Key words: diet model, diet selection, dry tropics, energy, expanding specialist, foraging behavior, granivorous birds, savannah, seasonality, secondary compounds, seed preference, water. [Behav Ecol 22: 639-647 (2011)]},
  author       = {Molokwu, Mary and Nilsson, Jan-Åke and Olsson, Ola},
  issn         = {1045-2249},
  language     = {eng},
  number       = {3},
  pages        = {639--647},
  publisher    = {Oxford University Press},
  series       = {Behavioral Ecology},
  title        = {Diet selection in birds: trade-off between energetic content and digestibility of seeds},
  url          = {http://dx.doi.org/10.1093/beheco/arr025},
  volume       = {22},
  year         = {2011},
}