Implications of temporal changes in forest dynamics on density, nest-site selection, diet and productivity of Tawny Owls Strix aluco in the Alps

Abstract

Capsule In the areas studied, Tawny Owls showed extreme flexibility and opportunism, occupying most available vegetation types and elevations below the tree-line. Aims To assess habitat relationships for the species so as to forecast the potential impact of habitat changes. Methods We censused a total of 321 territories in 12 study areas covering the regional variation in elevation and the associated heterogeneity in vegetation types and landscape configurations. Results The species occupied virtually all vegetation types and landscape configurations below the tree-line. Nests were mostly located on cliffs, but also in tree cavities, buildings, and stick nests of other raptors. Density varied from 12 to 60 territories/100 km2 and mean nearest-neighbour distance from 0.7 to 1.8 km, depending on the availability of broadleaved woodland. Compared to availability, nests were nearer to cliffs and had higher richness of habitat edges and vegetation types, which positively affected chick production. Diet composition varied widely according to habitat and was mostly dominated by Edible Dormouse Glis glis, voles and mice. Conclusion The conservation status of the species was satisfactory. Future habitat changes may favour an increase in density. Silvicultural practices encouraging more old trees with large cavities would further favour this opportunistic species.