© Marcel Burkhardt
Staggenborg, J., H. M. Schaefer, C. Stange, B. Naef-Daenzer & M. U. Grüebler (2017)
Time and travelling costs during chick-rearing in relation to habitat quality in Little Owls Athene noctua.
Ibis 159: 519–531
In many bird species, parents adjust their home-ranges during chick-rearing to the availability and distribution of food resources, balancing the benefits of energy intake against the costs of travelling. Over recent decades, European agricultural landscapes have changed radically, resulting in the degradation of habitats and reductions in food resources for farmland birds. Lower foraging success and longer foraging trip distances that result from these changes are often assumed to reduce the reproductive performance of parents, although the mechanisms are not well understood. We tested the behavioural response of chick-rearing Little Owls Athene noctua to variation in habitat diversity in an agricultural landscape. We equipped females with GPS loggers and received adequate range-use data for 19 individuals (6063–14 439 locations per bird). In habitats dominated by homogeneous cropland habitats, home-ranges were over 12 ha in size, whereas in highly diverse habitats they were below 2 ha. Large home-ranges were associated with increased flight activity (117% of that of birds in small home-ranges) and distances travelled per night (152%), increased duration of foraging trips (169%) covering larger distances (246%), and reduced nest visiting rates (81%). The study therefore provides strong correlative evidence that Little Owls breeding in monotonous farmland habitats expend more time and energy for a lower benefit in terms of feeding rates than do birds in more heterogeneous landscapes. As nestling food supply is the main determinant of chick survival, these results suggest a strong impact of farmland characteristics on local demographic rates. We suggest that preserving and creating islands of high habitat diversity within uniform open agricultural landscapes should be a key target in the conservation of Little Owl populations.
keywords: Athene noctua, farmland, foraging behaviour, habitat diversity, home-range size, parental costs.