Broedende Buizerds Buteo buteo en Haviken Accipiter gentilis in Boswachterij Veenhuizen: aantalontwikkeling, broedsucces en verstoring (1983-2007)

The Forestry of Veenhuizen in the northern Netherlands covers about 1800 ha, of which 865 ha consists of woodland (53.9% coniferous) (Table 1). The area used to have restricted access to the public, but this has recently changed in favour of recreation. Since 1983, Veenhuizen has been studied by a number of raptorphiles, using a mixture of field techniques (mapping territories, locating nests, climbing nesting trees, searching for pluckings, collecting moulted feathers, age-identifying individual breeders) (Table 2). The Common Buzzard increased from 6-16 pairs in 1983-94 to 20-30 pairs since then. The Goshawk showed more or less stable numbers throughout the 1980s and 1990s, but declined thereafter; the dip in the mid-1980s was due to systematic human persecution. Sparrowhawks Accipiter nisus declined from a high around 1990 to only a few pairs since the mid-1990s (Fig. 1). The latter may be caused by a change in woodland composition (fewer young stands available, cyclic thinning leading to opener woodland), and increased predation by Goshawks. These trends do not differ from those elswhere in the eastern and northern Netherlands. Breeding success of Buzzards and Goshawks, here defined as the proportion of territories successfully raising at least one young, was poor throughout the 1980s, then increased substantially to fluctuate around 60% in the 1990s and 2000s (Fig. 2, Appendix 1). The poor breeding success in the 1980s was largely due to intensive human persecution: poisoning incidents and deliberate disturbance of nesting sites were common practice in those days.