Hierarchical habitat selection by Eurasian Pygmy Owls Glaucidium passerinum in old-growth forests of the southern French Prealps

Abstract

Maintaining or restoring old-growth stand structures in mountain forests, including deadwood and snags provided by natural disturbances, is considered critical for the conservation of secondary cavity-nesting birds. Under current climate warming, old-growth mountain forests might become increasingly important for boreo-alpine species living in the southern part of their ranges. Here, we focused on hierarchical habitat selection by Eurasian Pygmy Owls Glaucidium passerinum in mixed mountain forests at their low latitude range limit in the southern French Prealps. We quantified Pygmy Owl habitat use at complementary hierarchical levels, from the local population to individual home ranges, by combining systematic playback counts and radio-telemetry. Mean home range sizes for breeding adult males covered 0.67 km2, ranging between 0.46 and 0.98 km2. We found evidence for Pygmy Owl habitat selection being a consistently hierarchical process, with (1) fir-dominated forests selected as the main habitat at the population level; (2) old-growth fir-dominated forest stands including edges with grassland gaps and karstic eroded areas selected at the home range level; and (3) amount of surrounding dead or decaying spruces increasing the occurrence probability of owl nesting cavities. Conserving Pygmy Owls at their low latitude range limit therefore requires the maintenance of old-growth mixed forests dominated by firs that provide these critical habitat features within a complex and heterogeneous landscape mosaic.