Gedrag van een overwinterende Giervalk Falco rusticolus in Zeeuws-Vlaanderen en het noorden van Oost Vlaanderen in de winter van 2011/12

Between 23 October 2011 and 18 March 2012, a first-year Gyrfalcon wintered in the southwestern Netherlands and adjoining parts of Belgium. A collation of records deposited at www.waameming.nl and www.waameming.be showed three separate kernels of activity, covering a total home range of some 28 by 10 km. The bird was often using electricity pylons as a sitting post. The separate kernels included largescale arable land with creeks (2x3 km, 5000-10.000 wintering waterbirds), largescale farmland on both sides of the Dutch-Belgian border (6x6 km) and large-scale grasslands, arable land and creeks (9xB km, in early spring 2012 average densities/km2 of 2-4 Hares Lepus europaeus, 4-6 male Pheasants Phasianus colchicus, 12-14 female Pheasants and 5-8 Grey Partridges Perdix perdix). First-hand prey captures were rarely witnessed, and involved Coot Fulica atra (2x) and Grey Partridge Perdix perdix (1x). However, the bird was seen hunting and feeding on a variety of mammals and birds, mostly ducks, geese, galliformes, Coots Fulica atra, Lapwings Vanellus vanellus and Woodpigeons Columba palumbus (Table 1). Agonistic interactions with raptors and corvids were frequently observed, with the Gyrfalcon on the receiving end of the encounters.