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Species distribution models analyse how species use different types of habitats. Their spatial predictions are often used to prioritize areas for conservation. Individuals may, however, prefer settling in habitat types of low quality compared to other available habitats. This ecological trap phenomenon is usually studied in a small number of habitat patches and consequences at the landscape level are largely unknown. It is therefore often unclear whether the spatial pattern of habitat use is aligned with the behavioural decisions made by the individuals during habitat selection or reflects actual variation in the quality of different habitat types. As species distribution models analyse the pattern of occurrence in different habitats, there is a conservation interest in examining what their predictions mean in terms of habitat quality when ecological traps are operating. Previous work in Belgium showed that red-backed shrikes Lanius collurio are more attracted to newly available clear-cut habitat in plantation forests than to the traditionally used farmland habitat. We developed models with shrike distribution data and compared their predictions with spatial variation in shrike reproductive performance used as a proxy for habitat quality. Models accurately predicted shrike distribution and identified the preferred clear-cut patches as the most frequently used habitat, but reproductive performance was lower in clear-cut areas than in farmland. With human-induced rapid environmental changes, organisms may indeed be attracted to low-quality habitats and occupy them at high densities. Consequently, the predictions of statistical models based on occurrence records may not align with variation in significant population parameters for the maintenance of the species. When species expand their range to novel habitats, such models are useful to document the spatial distribution of the organisms, but data on population growth rates are worth collecting before using model predi

Arthropods, and insects in particular, constitute important food resources for several higher trophic levels like birds. Their abundance and diversity is likely to differ between habitat types depending on the local conditions and resources. This may have important consequences for arthropod consumers that occupy structurally different habitat types. Most bird-focused studies address, however, habitats at the structural, vegetation-based level and disregard the presence of sufficient quantities and qualities of arthropod prey items. Here, we compare the quantity and quality of ground-dwelling and above-ground arthropods as food resources for early-successional birds between two structurally different human-modified habitat types sharing similar bird assemblages: low-intensity farmland areas and plantation forest clear-cut areas in the south of Belgium. Forest clear-cut patches constitute a novel habitat for so-called ‘farmland’ birds. Our results show that arthropod abundance is substantially higher in farmland than in forest clear-cuts, although arthropods are slightly larger in clear-cuts. Higher arthropod abundance is associated with higher ground-level temperature in farmland. Although both habitat types host the same spectrum of arthropod species, forest and farmland management practices induce different conditions for food quantity and, to some extent, food quality for insectivorous birds. We discuss the mechanisms behind the observed pattern of arthropod abundance and the fitness-related consequences of contrasting food availability in farmland and forest clear-cut habitats for early-successional bird species.

In human-modified environments, ecological traps may result from a preference for low-quality habitat where survival or reproductive success is lower than in high-quality habitat. It has often been shown that low reproductive success for birds in preferred habitat types was due to higher nest predator abundance. However, between-habitat differences in nest predation may only weakly correlate with differences in nest predator abundance. An ecological trap is at work in a farmland bird (Lanius collurio) that recently expanded its breeding habitat into open areas in plantation forests. This passerine bird shows a strong preference for forest habitat, but it has a higher nest success in farmland. We tested whether higher abundance of nest predators in the preferred habitat or, alternatively, a decoupling of nest predator abundance and nest predation explained this observed pattern of maladaptive habitat selection. More than 90% of brood failures were attributed to nest predation. Nest predator abundance was more than 50% higher in farmland, but nest predation was 17% higher in forest. Differences between nest predation on actual shrike nests and on artificial nests suggested that parent shrikes may facilitate nest disclosure for predators in forest more than they do in farmland. The level of caution by parent shrikes when visiting their nest during a simulated nest predator intrusion was the same in the two habitats, but nest concealment was considerably lower in forest, which contributes to explaining the higher nest predation in this habitat. We conclude that a decoupling of nest predator abundance and nest predation may create ecological traps in human-modified environments.

Habitat selection is an individual, behavioural, process during which organisms decide where to live and this decision-making ultimately affects their fitness. Organisms often exhibit preference for habitats that provide rewarding fitness consequences, but this adaptive link between habitat preference and habitat quality might become uncoupled in human-modified environments. Such ecological trapping has received both theoretical and empirical evidence, but the mechanisms leading to this form of maladaptive behaviour remain poorly understood. This thesis focuses on the habitat selection of a migratory bird, the Red-backed shrike (Lanius collurio), breeding in mixed farmland-forest landscapes of southern Belgium. Agricultural activities in farmland and harvesting practices in plantation forests provide structurally different open habitats for shrikes and other open-habitat wildlife. This offers the opportunity to test whether habitat selection is adaptive or if there is evidence for an ecological trap in this study species. A three-year dataset was collected to document habitat preference and habitat quality for the shrikes. A series of key environmental conditions and resources for the shrikes were sampled and compared between both habitat types to examine the mechanisms of habitat selection. Results indicate a preference for open areas in forest over farmland: the forest habitat was found to be valued as a territorial resource to a higher level by the shrikes and, on average, selected before farmland during the habitat selection phase. However, breeding shrikes showed lower reproductive performance in forest than in farmland. This ecological trapping pattern could be partly explained by two different functional components of habitat quality: predation rates and food resources. First, shrikes preferred to settle in the forest habitat with a lower amount of nest predators (i.e. corvids), but where nest predation rate was higher compared to farmland. Among the differen, (BIOL 3) -- UCL, 2013

1. 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 organ- isms, 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. 2. The Red-backed shrike (Lanius collurio) is a migratory bird that was shown to breed prefer- entially in forest plantation clearcuts where reproductive performance is however markedly lower than in the traditional farmland habitat. We examined whether differences in food avail- ability between forest and farmland habitats resulted in contrasting food provisioning to the offspring with, in turn, significant impact on the quality of the offspring. 3. 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 competi- tion for food was found in forest only. 4. 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 func- tional explanation for the mismatch between habitat preference and quality, and hence, for an ecological trap in the wild. 5. 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.

Preference measures are widely used in habitat selection studies to test an animal’s choice relative to particular habitat features, but most measures are subject to criticism as they fail to indicate the underlying behavioral motivation. Order of settlement on breeding sites has been proposed as an effective measure in migratory organisms, as it conceptually approaches a choice experiment. We tested the assumption that early red-backed shrikes (Lanius collurio) are more willing to defend their territorial resource than individuals arriving later. We earlier showed that shrikes arriving first settled in forest plantations that resulted in lower reproductive success compared to territories on farmland, suggesting an ecological trap. Therefore, individuals are expected to place higher value on the lower quality sites in forests. Within the context of resource valuation theory in animal contests, we used a simulated territorial intrusion experiment to measure territorial defense and to evaluate the perceived value of the territory during the settlement phase in both habitat types. Males arriving early were much more motivated to defend their territory than late birds. After correction for the disparity in the timing of arrival between habitat types, shrikes also more vigorously defended their territories in the forest habitat associated with the lowest reproductive returns. Although some resource valuation mechanisms remain unclear, our results show that early and late-arriving individuals strongly differ in behavioral motivation to hold their territorial resources. This study also demonstrates for the first time that organisms may exhibit a higher degree of territorial aggressiveness in a lower quality habitat.

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 pl