Central place foraging in a human-dominated landscape: how do common cranes select feeding sites?

Abstract

Human infrastructure and disturbance play an important role when animals select resources in human‐modified landscapes. Theory predicts that animals trade food intake against costs of movement or disturbance to optimize net energy gain and fitness, but other necessary resources may also constrain the decisions, e.g. when animals repeatedly need to return to a central location, such as a nest, waterhole or night roost. Central place foraging theory states that the probability of occurrence of an animal decreases with the distance to the central location while selectivity for food items or foraging sites providing high net energy gain should increase with distance. We studied foraging patterns of common cranes Grus grus feeding in an agricultural landscape adjacent to a wetland to which they return for night roost. We used availability of spilled grains on harvested fields and distance to human settlement as proxy for site quality (i.e. increased likelihood of increased net energy gain with increased food availability and less disturbance). As predicted by theory, our results clearly show that cranes were more likely (more than twice as high resource selection function scores) to select foraging sites close to roosts. However, contrary to predictions, the selection of high quality sites in terms of high food availability decreased with distance to roost sites. Nevertheless, our results indicate that cranes were more likely to select sites with low risk of human disturbance far from roost sites, and were more tolerant to disturbance close to roost sites. How different species respond to the local and environmental conditions will increase the understanding of the species’ resource requirement, and also where in the landscape to prioritize conservation or management actions (e.g. mitigation of human disturbance and crop damage prevention to sustain agricultural production).