Global Ecology and Conservation (Dec 2023)
Extensive dune grasslands largely lacking human disturbance are an important refuge for a vole-dependent raptor
Abstract
Agricultural intensification and abandonment have led to a dramatic decrease of semi-natural grasslands such as low-intensity pastures and hay meadows. The Short-eared owl (Asio flammeus) is a ground-nesting raptor of open grasslands that has severely suffered from these changes. We studied the habitat preferences of this umbrella species of open grasslands in its last permanent breeding area in Germany (East Frisian Islands, southern North Sea). We analysed the breeding-territory preferences based on 576 territories on six of the islands. Moreover, we assessed nest-site preferences of 13 breeding pairs on the German abundance hot spot, the island of Spiekeroog. Our investigation revealed that the Short-eared owl strongly preferred open dunes for breeding, especially dune grasslands. By contrast, built-up areas and small stands of trees were avoided. For nest-building, microhabitats with a high cover of the herb layer and litter resulting in tall vegetation were favoured. By contrast, the vegetation in the wider surrounding of the nest was characterised by more bare ground and shorter vegetation but still a high cover of the herb layer and litter. In conclusion, our study highlights the prime importance of extensive open grasslands with a pronounced litter layer and largely lacking human disturbance as breeding habitats for the Short-eared owl. At the nesting site, we suggest that tall and dense vegetation with a high cover of litter (i) might enhance concealment and (ii) causes a favourable microclimate by protecting fledglings against adverse weather conditions. In the wider surrounding of the nest, shorter vegetation with a pronounced litter layer (i) improves fledgling mobility, (ii) fosters vole abundance and (iii) increases prey accessibility.
