Roofvogels in de duinen bij Castricum in 2000-15

The number of successful breeding Goshawk pairs Accipiter gentilis in the dunes near Castricum (1058 ha) decreased from 2.5 per year in 2000-07 to 1.6 per year in 2008- 15. This might be related to a decrease in food supply. Other adverse changes include disturbance from a growing number of bikers, recreation in combination with water extraction, and nature management. The decrease in the number of successful breeding pairs of Sparrowhawks Accipiter nisus from 3.0 per year in 2000-03 to 1.0 per year in 2012-15 is likely due to predation by Goshawks (perhaps including predation by Buzzards Buteo buteo and Pine Martens Martes martes). Predation of Sparrowhawks by Goshawks was substantiated. Predation by Buzzards and Pine Martens is likely, given the negative correlations between the number of successful breeding pairs of Sparrowhawks and the number of successful (breeding) pairs of Buzzards and Pine Martens. The first successful breeding attempts of Honey-buzzard Pernis apivorus were recorded in 2008-11, years with few successful breeding Goshawk pairs (a serious threat to Honey-buzzards, as shown by a negative correlation between number of successful breeding pairs of Goshawks and the number of successful breeding pairs of Honey-buzzards). The number of successful breeding pairs of Buzzards increased from 4.0 per year in 2000-03 to 7.5 per year in 2004-07. In 2008-11, numbers temporarily dropped to 5.5 pairs annually. This decline was probably due to a decrease in rodent numbers in those parts of the forest that were grazed by Scottish Highlanders from 2009 onwards. In 2012, however, Buzzards were more successful than ever before, probably related to clear-felling along forest trails to create ecotones. Thereafter, the number of successful breeding pairs of Buzzards returned to the level of 2004-07.