Abstract
Recent research reports that many populations of species showing a wide trophic niche (generalists) are made up of both generalist individuals and individuals with a narrow trophic niche (specialists), suggesting trophic specializations at an individual level. If true, foraging strategies should be associated with individual quality and fitness. Optimal foraging theory predicts that individuals will select the most favourable habitats for feeding. In addition, the “landscape heterogeneity hypothesis” predicts a higher number of species in more diverse landscapes. Thus, it can be predicted that individuals with a wider realized trophic niche should have foraging territories with greater habitat diversity, suggesting that foraging strategies, territory quality and habitat diversity are inter-correlated. This was tested for a population of common kestrels Falco tinnunculus. Diet diversity, territory occupancy (as a measure of territory quality) and habitat diversity of territories were measured over an 8-year period. Our results show that: 1) territory quality was quadratically correlated with habitat diversity, with the best territories being the least and most diverse; 2) diet diversity was not correlated with territory quality; and 3) diet diversity was negatively correlated with landscape heterogeneity. Our study suggests that niche generalist foraging strategies are based on an active search for different prey species within or between habitats rather than on the selection of territories with high habitat diversity.
Highlights
Optimal foraging theory predicts that individuals will select the most favourable habitats for feeding to minimize energy expenditure and maximize fitness [1, 2]
The lineal models (LM) exploring the relationship between occupancy and TLH showed a curvilinear correlation (TLH, F1,58 = 5.44, P = 0.023, TLH2, F1,58 = 5.54, P = 0.02; Fig 2)
Landscape heterogeneity promotes an increase in species diversity (LHH), and a higher diversity of habitats in kestrel territories should provide them with a greater diversity of prey in the diet
Summary
Optimal foraging theory predicts that individuals will select the most favourable habitats for feeding to minimize energy expenditure and maximize fitness [1, 2]. The classical niche theory predicts a positive correlation between habitat diversity/heterogeneity and diversity of species [3,4,5,6]. This is the landscape heterogeneity hypothesis (LHH) [3, 4], and is based on the idea that more heterogeneous landscapes with higher habitat diversity may provide more diverse ways of exploiting the environmental resources (niches) than more homogenous landscapes, allowing exploitation by a greater number of species [5, 7]. Raptor Species Relationship between Diet Diversity and Habitat competitividad (MIMECO) BES-2011-043956 (http:// www.mineco.gob.es/)
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