Roofvogels van de Amsterdamse Waterleidingduinen in 2015, met opmerkingen over het beheer van de duinen

From 1961 onwards, the Amsterdamse Waterleidingduinen (3400 ha, of which 600 ha forested and 200 ha of canals; the area is used to infiltrate water for the production of drinking water) have been systematically surveyed for owls and raptors. Annually, all nests are located and visited to establish clutch size, to ring nestlings and to collect biometric data. Nests of Tawny Owls Strix aluco are visited monthly, especially to obtain detailed information on turnover, reproductive performance and dispersal. Whenever possible, prey remains and pellets are collected on/near nests to obtain information on diets. In 2015, the survey revealed territories of Tawny Owl (15, of which 9 with nest, of which 5 were successful in raising a total of 12 chicks), Buzzard Buteo buteo (resp. 19, 18, 15 and 28), Goshawk Accipiter gentilis (resp. 11, 8, 5 and 10), Sparrowhawk A. nisus (resp. 2, 1, 1 and 0), and Honey-buzzard Pernis apivorus (resp. 1, 1, 1 and 2). Over the years, but especially since large-scale management was implemented (including intensive grazing with cattle and sheep, removing ground cover, cutting down conifer plantations and cultivating the top soil), raptors and owls have been in decline. For Tawny Owl, this decline was accompanied by increased mortality and high turnover rates. The declining biodiversity was also visible in the species which constitute the main food supply for raptors, with strong declines in rodent populations (due to intensive grazing with cattle) and the population of breeding birds (since grazing started, a loss of 70% in numbers).