Distribution, density, diet and productivity of the Scops Owl Otus scops in the Italian Alps.

摘要

The Scops Owl Otus scops is probably the least known European owl. We surveyed Scops Owls in the Trento region (6200 km2) of the central-eastern Italian Alps between 1995 and 2003 and we intensively monitored a subpopulation in a 50-km2 plot between 2000 and 2003. In the whole region, we found 81 territories concentrated in 21, low-elevation 100-km2 quadrats. Most territories were associated with villages surrounded by extensively managed grassland (79%), arid areas with rocky outcrops and xerophytic vegetation (12%) and/or large urban areas and parks (6%). In the 50-km2 plot, density varied between 52 and 64 territories/100 km2 annually. Territories were either solitary or clumped in loose colonies of 2-7 pairs. In contrast to previous studies, most nests used for laying were in holes and cracks of buildings (95%, n=20). This may have been favoured by thermal and foraging advantages, but also involved some costs, such as predation by domestic cats and collision with cars. Median laying date was 29 May (n=16) and the mean number of fledged young was 1.37 (n=30), 1.95 (n=21) and 2.00 (n=20) per territorial, breeding and successful pair, respectively. The diet was dominated by grasshoppers of the family Tettigoniidae. Compared to previous studies, this population showed medium to high density and low productivity. The species seems to be dependent on traditional, extensive agro-pastoralism and the main conservation threats include habitat loss through land abandonment and consequent forest expansion, which are probably best halted through subsidy schemes. From our results and published data, we estimate the population of the Scops Owl in the Italian Alps at 230-500 territories. There is an urgent need for further data on this largely overlooked species, especially from its Mediterranean strongholds.