Пернатые хищники и их охрана (Apr 2016)
The Ecology of the Ural Owl at South-Western Border of Its Distribution (Slovenia)
Abstract
In Slovenia the Ural Owl (Strix uralensis) is on its south-western limit of distribution and belongs to the southern subspecies Strix uralensis macroura. Dark coloured owls are characteristic for this subspecies and represent between 5 to 15% of the population. Slovenian breeding population size is estimated at 400 to 700 pairs. The densities of territories ranges between 0.9 to 13.4 territories per 10 km2, and the highest are reached in mountain forests of southern Dinaric region. In the forests with dominant deciduous trees, e.g. Beech (Fagus sylvatica) and Pedinculate Oak (Quercus robur), the breeding densities are significantly higher than in the forests with higher proportion of coniferous trees, e.g. Norway Spruce (Picea abies). The species does not select specific altitude and throughout Slovenia it occurs between 150 and 1600 m a.s.l. The most of the nest found at natural nest-sites were in tree holes or semi-holes (56%) and at the tree stumps (20%). Nest boxes were occupied less frequently in Slovenia with occupancy rate of 29%. At least in mountain regions breeding begins quite late, between 15 March to 21 June. Average clutch size is 3.3 ± 1.0 eggs per nest. About 80% of all nests are successful raising at least one young. The diet shifts significantly between breeding and non-breeding period due to the seasonality in prey availability. According to the biomass the most important prey in breeding period are mice (Muridae), voles (Arvicollidae) and mole (Talpa europaea), but in the non-breeding period voles and dormice (Gliridae) predominate. Large Fat Dormouse (Glis glis) seems to have very important role in the post-breeding period, but not in the breeding period due to its dormancy. As a large forest-dwelling predator the Ural Owl shapes the raptor community in the forest by excluding mezopredator species, as Tawny Owl (Strix aluco), what allows smaller raptors, e.g. Boreal Owl (Aegolius funereus) to expend their ranges to lower elevations. However, this pattern is not general through the whole Ural Owl range since species ecology and morphology could be regionally quite different, therefore ecological studies from different parts of Ural Owl range are needed.
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