Grauwe Kiekendieven Circus pygargus in Nederland in 2000

In 2000, 44 pairs of Montagu’s Harriers were located in The Netherlands, the highest number since 1980 (Fig. 2). The distribution was concentrated in farmland (mainly alfalfa and winter wheat) in Groningen and Flevoland and in natural habitats in Lauwersmeer (Fig. 1). Mean onset of laying was 19 May (range 4 May-2 June, n=23), mean clutch size 3.6 (range 1=6, SD=1.0, n=20) and mean brood size 2.6 (ringing age, range 1-4, SD=1.0, n=25), i.e. comparable with results during 1990-99 (Table 1). Among 829 prey items collected on and near nests. Common voles Microtus arvalis and small passerines dominated, but the variety of prey species suggests a wide use of available food resources (Appendix 1, Fig. 3). Nest protection and set-aside are considered major factors in the slow but steady increase of the Dutch population (Fig. 4), but this needs further substantiation.