Evaluating the influence of diet-related variables on breeding performance and home range behaviour of a top predator
The relationships between prey abundance, diet and individual fitness are complex, especially in vertebrate top predators, such as eagle owls. Superpredation, diet diversity, rat biomass and rabbit mean weight were the most important variables when analysing reproductive parameters of eagle owls, suggesting that less diverse diets with greater rabbit biomass percentage may benefit reproductive performance, whereas rat biomass percentage is apparently associated with greater variation of breeding success. On the other hand, edge density was the most relevant factor determining the variation in home range behaviour. Our results suggest that when rabbits are less available eagle owls may increase home range size in order to obtain alternative prey, increasing at the same time their dietary diversity, which may also require higher movement speed.

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Erkki Korpimäki