Gebruik van Zuid-Flevolandse bossen door Wespendieven Pernis apivorus van de Veluwe

On 17 July 2001 (9.40-12.50 hr) Horsterworld, a deciduous woodland in the reclaimed polder of Zuidelijk Flevoland (about 6000 ha, including Hulkesteinse Bos), was scanned for Honey Buzzards from a high tower in the centre. Zuidelijk Flevoland came into existence in 1968, when it was reclaimed from the Ijsselmeer. The soil consists of marine clay. Woodlands, mainly consisting of deciduous trees such as Quercus robur, Fraxinus excelsior, Populus spp. and Fagus sylvatica, were planted between 1973 and 1985. Horsterwold lies at a distance of c. 10-12 km from the extensive forests on the sandy Veluwe, separated from it by a 1 -4 km wide strip of water (Nuldemauw and Wolderwijd) and farmland along the edge of the Veluwe (4-5 km wide). The Veluwe is considered typical breeding habitat for Honey Buzzards, but breeding in the newly created polder forests of Zuidelijk Flevoland is not yet proven, despite some observations suggesting the use of these areas by Honey Buzzards from at least 1994 onward. Four, probably different, Honey Buzzards were observed during the short observation period, none of which behaved in the manner of a breeding bird having a nest in the area (Fig. 1). An adult male ascended for a short while, only to descend again after 1 km (typical foraging behaviour). Three other birds ascended from Horsterwold, gained height and crossed the lake which separates the reclaimed polder from the Veluwe, without reluming One of these birds, an adult female, transported a prey item. Prey transfers of Honey Buzzards are always directed toward a nest, indicating that this bird must have had a nest on the Veluwe. As Honey Buzzards in The Netherlands nest in large forests or in densely forested areas, the distance covered by this bird between the site of prey capture in Horsterwold and the nearest suitable breeding site on the Veluwe must have been at least 10 km. Neither the present observations, nor data gathered during systematic mapping in the previous months, indicated that Honey Buzzards breed in Horsterworld. It should be noted that apparently some Honey Buzzards from the sandy Veluwe preferred to forage in the clayey polder woodlands, an unexpected outcome for a bird known to mainly forage on ground-dwelling social wasps.