Abstract
In human-altered environments, organisms may preferentially settle in poor-quality habitats where fitness returns are lower relative to available higher-quality habitats. Such ecological trapping is due to a mismatch between the cues used during habitat selection and the habitat quality. Maladaptive settlement decisions may occur when organisms are time-constrained and have to rapidly evaluate habitat quality based on incomplete knowledge of the resources and conditions that will be available later in the season. During a three-year study, we examined settlement decision-making in the long-distance migratory, open-habitat bird, the Red-backed shrike (Lanius collurio), as a response to recent land-use changes. In Northwest Europe, the shrikes typically breed in open areas under a management regime of extensive farming. In recent decades, Spruce forests have been increasingly managed with large-size cutblocks in even-aged plantations, thereby producing early-successional vegetation areas that are also colonised by the species. Farmland and open areas in forests create mosaics of two different types of habitats that are now occupied by the shrikes. We examined redundant measures of habitat preference (order of settlement after migration and distribution of dominant individuals) and several reproductive performance parameters in both habitat types to investigate whether habitat preference is in line with habitat quality. Territorial males exhibited a clear preference for the recently created open areas in forests with higher-quality males settling in this habitat type earlier. Reproductive performance was, however, higher in farmland, with higher nest success, offspring quantity, and quality compared to open areas in forests. The results showed strong among-year consistency and we can therefore exclude a transient situation. This study demonstrates a case of maladaptive habitat selection in a farmland bird expanding its breeding range to human-created open habitats in plantations. We discuss the reasons that could explain this decision-making and the possible consequences for the population dynamics and persistence.
Highlights
Habitat selection theory generally assumes that individuals are able to make optimal settlement decisions, thereby selecting the highest-quality habitats that are available in a heterogeneous landscape to maximize their fitness returns [1]
Using the Red-backed shrike as a model organism that occupies both habitat types in a mosaic of farmland and woodland sites, we demonstrate a preference for Spruce plantations over farmland sites, even though reproductive performance was higher in farmland
As order of settlement and distribution of dominant individuals are considered as individuallevel measures of habitat preference [19], these results indicate a preference for the novel woodland environment rather than for the traditionally used farmland
Summary
Habitat selection theory generally assumes that individuals are able to make optimal settlement decisions, thereby selecting the highest-quality habitats that are available in a heterogeneous landscape to maximize their fitness returns [1] Such adaptive habitat choices are expected to produce an ideal free distribution [2] or similar patterns [3]. Many studies have found strong empirical support so far [5,6,7], individuals are not always able to directly judge habitat quality in terms of fitness returns and, instead have to rely on environmental cues to guide their settlement decisions [8]. It has been shown that these organisms may rely upon a host of proximate cues reflecting the environmental conditions that will affect fitness, such as the vegetation structure and phenology [11], food availability [11,12,13], anti-predation shelters [14] or social attraction [15]
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