Foerageergedrag en voedsel van Drentse Ooievaars Ciconia ciconia

In 2012, a pair of White Storks successfully raised two chicks near Wateren in western Drenthe, the first breeding attempt in decades. These birds were recorded foraging up to 2 km from the nest, possibly as far as 3 km (but birds not individually identified, hence of uncertain status). Compared to habitats available, White Storks strongly preferred foraging in recently mowed ‘natural’grasslands in a brook valley with a peat-dominated soil (‘natural’ meaning: grasslands set aside, and being mowed for the first time late in the season, i.e. late August). These grasslands showed a high density of Common Voles Microtus arvalis and Moles Talpa europaea, on top of a diverse arthropod fauna (Table 2). Foraging Storks were taking small prey, presumably mosdy insects. Out of 273 successful catching attempts, 18 locusts, 36 insects, 22 earthworms, 6 earthworms/ leatherjackets, 6 beetles, 1 slug and 2 Common Frogs were identified as prey. These prey were taken whilst slowly walking the fields, pecking prey from the vegetation or the ground. One Stork used a heron-like foraging strategy, i.e. standing still and waiting for voles to show up. Foraging success averaged 2.94 prey/minute, ranging from 0 to 7.5/min (Table 1). Apparendy, mowing in grassland is important as it attracted White Storks (and a range of other vole-eating predators and insectivorous passerines) from afar. Sequential mowing may enhance the availability of prey to White Storks through time.