Understanding the rules of habitat selection and the individual behavioural routines in the home-range is crucial for developing evidence-based conservation action. We investigated habitat selection and range use of adult little owls Athene noctua in relation to landscape configuration, habitat structure and resource distribution. We determined the preference of habitat structures by VHF-telemetry. Large-and fine-scale distribution patterns of volesthe main prey during the breeding season were assessed by transect counts of signs of vole presence. An experiment using artificial perches was carried out to determine the fine-scale adjustment of the owls' range use in relation to prey abundance and vegetation height. Habitat selection and resource exploitation by little owls were structured at all spatial levels: (1) at the landscape scale, orchards were highly preferred over other areas. This accords with the patchy large-scale occurrence of voles, which were absent in cropland, but abundant in orchards and grassland; (2) within home-ranges, the spatial distribution of voles was highly inhomogeneous and structures with high prey abundance were used over-proportionally; (3) at the scale of foraging sites, little owls preferred patches with low vegetation over those with high prey abundance, establishing that prey availability is the crux. The results suggest that all levels of habitat selection and range use were related to farming practices and affected by current cultivation. Conservation measures should focus on the conservation and restoration of orchards on the landscape level and habitat management measures should focus on grasslandsthe main food providersby creating a mosaic of patches with short grass and tall grass. Together with other habitat structures providing food resources such as field edges, wildflower areas and structures facilitating access to prey, the quality of habitat patches in terms of food availability may be highly improved.
Background For resident birds of prey in the temperate zone, the cold non-breeding period can have strong impacts on survival and reproduction with implications for population dynamics. Therefore, the non-breeding period should receive the same attention as other parts of the annual life cycle. Birds of prey in intensively managed agricultural areas are repeatedly confronted with unpredictable, rapid changes in their habitat due to agricultural practices such as mowing, harvesting, and ploughing. Such a dynamic landscape likely affects prey distribution and availability and may even result in changes in habitat selection of the predator throughout the annual cycle. Methods In the present study, we (1) quantified barn owl prey availability in different habitats across the annual cycle, (2) quantified the size and location of barn owl breeding and non-breeding home ranges using GPS-data, (3) assessed habitat selection in relation to prey availability during the non-breeding period, and (4) discussed differences in habitat selection during the non-breeding period to habitat selection during the breeding period. Results The patchier prey distribution during the non-breeding period compared to the breeding period led to habitat selection towards grassland during the non-breeding period. The size of barn owl home ranges during breeding and non-breeding were similar, but there was a small shift in home range location which was more pronounced in females than males. The changes in prey availability led to a mainly grassland-oriented habitat selection during the non-breeding period. Further, our results showed the importance of biodiversity promotion areas and undisturbed field margins within the intensively managed agricultural landscape. Conclusions We showed that different prey availability in habitat categories can lead to changes in habitat preference between the breeding and the non-breeding period. Given these results we show how important it is to maintain and enhance structural diversity in intensive agricultural landscapes, to effectively protect birds of prey specialised on small mammals.
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