Grauwe Kiekendieven Circus pygargus in Nederland in 2006

In 2006, 39 pairs were recorded, of which 29 in Groningen, 6 in Flevoland, 2 in Friesland and 2 in Drenthe. Out of 31 nests, 12 failed before fledging; the remaining nests raised 47 chicks. Most young were (colour)ringed. Resightings and photographs of birds colour-ringed in previous years showed dispersal distances of up to 140 km in 2006 (Table 1). The majority of nests was built in winter wheat, which necessitated protective measures during harvest; only two pairs nested in semi-natural habitat. With 46% of the prey list, voles were an important prey species in numbers (N=2054 prey items, based on plucks and pellets; Appendix 1), but leverets were important in terms of biomass. One particular pair nested near a set-aside project, where the high density of passerines may have been attractive. Three males were radio-tagged to study habitat use and hunting efficiency. Four adult females and two adult males were, moreover, equipped with a satellite transmitter, of which five could be followed into West Africa (Senegal, Mauritania, Mali). The whereabouts of these birds can be tracked on the internet (www.grauwekiekendief.nl).