Opmerkelijk goede broedresultaten van Sperwers Accipiter nisus in een Veluwse boswachterij

In mainly coniferous forest at Garderen in the Veluwe district (1984 ha) 8 territories of Sparrowhawk were located, 7 of which contained nests in which eggs were laid. Mean onset of laying was 30 April, mean clutch size was 5.0 eggs and 6 nests fledged at least 23 young (3.3/successful nest). Only a single nest was depredated (in egg stage), despite the presence of 6 active nests of Goshawks. Elsewhere on the Veluwe, nesting success was much lower: at Nunspeet (2400 ha) only 2 out of 12 nests were successful in 1995-98 (successful nests restricted to 1998; Willem van Manen) and at Planken Wambuis (1965 ha) only 3 out 17 nests in 1990-98 produced fledglings (Rob G. Bijlsma). In most cases, Goshawk predation was the cause of failure. The Veluwe offers poor feeding conditions for Goshawks, especially since the availability of Wood Pigeons and Racing Pigeons has declined; raiding nests may have become a partial substitute for ‘normal’ prey. The situation at Garderen is different, as most pairs of both Sparrowhawk and Goshawk nest in the vicinity of human habitation with its abundance of House Sparrows (higher proportion of House Sparrows in the diet of Sparrowhawks nesting close to villages) and pigeons (main prey of Goshawks). This enables female Sparrowhawks to stay near their nest during the nestling period (nest protection, although it is unlikely that it effectively deters Goshawks), whereas Goshawks may have no need to raid nests in the forest.