Buizerd Buteo buteo en Boommarter Martes martes in het Noord-Kennemerlands Duin

The number of successful breeding attempts of Buzzards Buteo buteo in Noordhollands Duinreservaat near Castricum increased from 2—4 in 2000-02 to 8-9 in 2006-08. Since then, numbers decreased to 5-6 in 2009-10 and 3 in 2011. Probably, the number of successful breeding attempts is correlated with food supply. Disturbance of nests and (since 2006) possibly egg and/or chick predation by Pine Martens Martes martes also have a negative impact. In 2011, for the first time a den with young Pine Martens was found in the dunes north of the Noordzeekanaal. The Buzzard pair near Castricum, in which territory this Pine Marten den was found, failed to raise nestlings in 2010 and 2011. In 2009 a single Buzzard chick was raised in this territory; its sibling disappeared early in the chick stage. In this nest, and based on measurements of the chicks, the second egg must have been laid more than three weeks after laying of the first egg, which is highly unusual.