Spatio-Temporal Patterns of Owl Territories in Fragmented Forests are Affected by a Top Predator (Ural owl)

Abstract

Competitive intraguild interactions can modify the spatial and temporal territory use of predators, e.g., this phenomenon was reported among species of owls (Strigidae). This study made use of owl guild present in fragmented forests in southern Poland to investigate how the occurrence of the dominant Ural owl affects the territory distribution of subordinate (in descending order): tawny owl, boreal owl and pygmy owl. Surveys carried out in 2014–2015 showed that the tawny owl decreases in density and the distances between its territories increase in sympatry with Ural owl. The tawny owl increases in abundance during the non-breeding season, in particular in sympatry with the Ural owl, where young tawny owls try to settle within territories of the Ural owl. The distribution of the boreal owl territories was found to be random with respect to the tawny owl, but territories were clustered in space with the Ural owl territories, which suggests that the boreal owl distribution tends to follow the availability of suitable nesting places rather than the avoidance of the tawny owl. The distribution of the pygmy owl territories was random with respect to the Ural owl, but clumped with respect to the tawny owl, as both species occupied fir-spruce stands avoided by the Ural owl. In summary, this study broadens the basic knowledge about spatio-temporal relations within the owl guild by showing that the occurrence of the dominant Ural owl is a substantial factor in shaping the distribution of owls in fragmented forests.