Long- and short-term state-dependent foraging under predation risk: an indication of habitat quality
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Animals living in environments of different quality will have different expectations of their future reproductive success and survival. This may affect the individual's risk-taking behaviour as manifest in the cost of predation. We investigated the foraging behaviour of starlings, Sturnus vulgaris, when perceived predation risk varied between patches. Short-term food availability varied between treatments and long-term differences in perceptions of environmental quality varied between groups of individuals. This corresponds to variation in the three components of the cost of predation (P): the predation risk (p); the change in reproductive value with energy gain (partial derivativeF/partial derivativee); and the reproductive value or fitness factor (F). The birds showed that they experienced a higher cost of predation while using the risky food patches (mu component) and in the high food treatment (partial derivativeF/partial derivativee component). Furthermore, birds from a high-reward habitat revealed a higher P than birds from a poor habitat (F component). The results show that the costs of predation are possible to tease apart by using behavioural indicators. The method presented allows measurement of fitness prospects of individuals, which may have consequences for conservation, for example, to identify low-quality habitat. (C) 2002 Published by Elsevier Science Ltd on behalf or The Association for the Study of Animal Behaviour.