Gedrag en prooikeuze van vier sperwerparen Accipiter nisus in Zoetermeer

Four Sparrowhawk pairs breeding in the town of Zoetermeer (western Netherlands) were studied during the breeding season of 2005. Three pairs nested in parks close to farmland (130-300 m, nearest farms at 340-515 m), the fourth pair nested in an urban environment 955 m away from the nearest farmland (Figure 1, Table 1). Mean nearest neighbour distance was 930 m (range 270-1400 m). All pairs nested successfully in deciduous trees ( Salix 2x and Crataegus 2x), with up to 5 young per nest. Most females behaved secretively in the presence of man, but intensity of alarm calling increased during the nestling period. Females stayed near the nest during most of the breeding cycle (recorded during 46 out of 49 nest visits throughout the nesting cycle), possibly an anti-predator behaviour. Although Goshawks Accipiter gentilis are still absent in Zoetermeer, Carrion Crow Corvus corone and Magpie Pica pica were local breeding birds and were chased by male and female when showing up in the vicinity of their nest. After fledging in late June and early July, young were still fed on the nest for some time and stayed nearby for several weeks (often heard begging or seen flying). The analysis of pluckings revealed individual variations in hunting habitats of male Sparrowhawks, some foraging in (sub)urban habitats, another (Nest 3) clearly focusing on farms in nearby farmland (see preponderance of Hirundo rustica, Motacilla alba and Passer domesticus; Table 2). More than 50% of all prey items consisted of only four species: House Sparrow Passer domesticus (16.0%), Great Tit Parus major (15.3%), Bam Swallow Hirundo rustica (11.1%) and Blue Tit P. caeruleus (10.4%).