Opzettelijke verstoring van broedende roofvogels in Nederland in 2003

During countrywide research on the breeding biology of raptors, slightly over 3500 nests were found and checked in 2003, of which 81 were labelled as having been deliberately disturbed by humans. Most nests were destroyed in the province of Friesland (Fig. 1), the side-effect of a thriving tradition of meadow bird protection. Elsewhere in The Netherlands, persecution through nest destruction is also common practice but probably of a more localised occurrence. Species most affected are Eurasian Marsh Harrier (9.8% of all nests found were destroyed), Northern Goshawk (4.0%) and Common Buzzard (2.4%), i.e. large raptors that prey on small game and meadow birds (Table 1). When the 3500 nest cards form a representative sample of the Dutch raptor population (likely, given the geographical distribution of the cards and the high proportion of the Dutch raptor populations being sampled), an estimated total of at least 340 raptor nests must have been destroyed in 2003. Raptor persecution is illegal, hence difficult to detect. An indirect way to trace areas with a high incidence of persecution is to look at regional variations in nest success of Goshawks. In the absence of persecution, normally some 75% of Goshawk nests is successful. If this proportion is considerably smaller, likely human persecution is involved. During 2003, eight such regions were identified (nest failure rate among Goshawks varying between 50 and 83%); in the same regions high failure rates were also recorded for Common Buzzards (Table 2). Several of these regions have a history of raptor persecution, with a consistent poor nest success in Goshawks (and partly also in Common Buzzards, Table 3). This method of comparison allows a quick assessment of the extent of raptor persecution in large regions.