Habitat‐dependent prey availability and offspring provisioning explain an ecological trap in a migratory bird

Abstract

Summary Ecological trapping implies a preference for low‐quality habitats over higher‐quality options. Although such a maladaptive decision‐making has been shown in a range of organisms, the mechanisms that underlie this habitat selection pattern often remain unidentified. We tested in a human‐modified environment whether food availability and food use of a migratory species operate as functional drivers of an ecological trap. The Red‐backed shrike (Lanius collurio) is a migratory bird that was shown to breed preferentially in forest plantation clearcuts where reproductive performance is however markedly lower than in the traditional farmland habitat. We examined whether differences in food availability between forest and farmland habitats resulted in contrasting food provisioning to the offspring with, in turn, significant impact on the quality of the offspring. Invertebrate prey items for shrikes were 41% more abundant in farmland, and prey size was 6% larger in forest habitat. Opposite to the pattern of prey size availability, larger prey items were delivered to the offspring in farmland than in forest habitat. Feeding visits by the parents were 22% more frequent in farmland, and evidence of strong among‐nestling competition for food was found in forest only. This study demonstrates the existence of food limitation for an organism in a habitat type associated with high preference but low reproductive performance. This result offers a functional explanation for the mismatch between habitat preference and quality, and hence, for an ecological trap in the wild. Beyond the case of migratory birds, this study draws attention to the point that human‐modified environments may lead to a biased perception of habitat quality relative to food availability and may induce an ecological trap for organisms that allocate only a limited time budget to habitat selection decision‐making.