Het verzamelen en clusteren van wespendiefwaarnemingen Pernis apivorus

Honey Buzzard movements were mapped in July and August by observing birds from high vantage points (treetops, especially Dougals Fir and Common Silver Fir, cf. fig.l). Individual recognition (by plumage variation, sex differences and moult) is the magic word in this method. Food transportation was instrumental in finding nests, individual recognition in identifying territories. In the forestry of Dwingeloo (c. 1400 ha) 80 fieldhours in May-August 1991 resulted in only five observations of Honey Buzzards, whereas 24 hours and 20 minutes of "tree topping" in August resulted in 31 observations, indicating four territories and two nests (fig. 3). The function of wing-clapping is still unclear. Rob Bijlsma, Arend van Dijk, Bert Dijkstra, Albert Henckel, Joop Kleine, Hans Pietersma, Maria Quist en Matthijs Smaal waren behulpzaam bij het veldwerk, Rob Bijlsma becommentarieerde het manuscript.