Habitat selection and patterns of distribution in a hierarchic forest owl guild

Abstract

Patterns of segregation were studied in a size-structured forest owl guild with the largest Ural Owl Strix uralensis, intermediate Tawny Owl Strix aluco, and the smallest Tengmalms Owl Aegolius funereus, by comparing habitat selection and patterns of dis-tribution. Data on owl territories were collected between 1998 and 2003 on Mt. Krim, North Dinaric Alps, central Slovenia, using the playback method. The Ural Owl was the dominant species, occupying the largest part of its optimal habitat, i.e. its fundamental niche. The Tawny Owl had the widest habitat niche. Due to negative interactions it se-lected refugial areas free of Ural Owls, which were in lowlands only, where human influ-ences prevent Ural Owls from settling. Tengmalms Owl was the most specialised in hab-itat selection. Its territories were on high altitudes, within those of the Ural Owl. They in-habited similar habitats but we found no indications of interactions between them. In con-trast, Tawny and Tengmalms Owls were highly segregated in habitat and in space, due to distinctive negative interactions. Based on these results, we propose the following hy-pothesis: Tengmalms Owl benefits from the presence of Ural Owls, which creates Tawny Owl free areas; this association does not affect the Ural Owl. This could be the first case of positive interactions in a predatory guild, i.e. a specific type of commensalism.