Reproductie van Kievit Vanellus vanellus en Scholekster Haematopus ostralegus in gangbaar landbouwgebied bij Ravenswoud in 1997

Reproductive success of Lapwings and Oystercatchers was studied on 122 ha of farmland on sandy soil (17% maize, 30% potato, 10% sugarbeet and 43% grassland). All parcels were welldrained and intensively farmed. Grassland was completely ignored as a breeding site by both species (although becoming important during the chick stage; Table 3), whereas potato-fields were favoured (Table 1). Of 25 Lapwing clutches with known outcome, 22 hatched successfiilly (77 chicks); in Oystercatcher this was 4 out 5, with 9 chicks (Table 2). This high nest success was achieved through specific nest protection; nest success would have been substantially lower without such measures taken. Chick survival (till fledging) was very low: 0% in Oystercatchers and 9 fledglings in 5 Lapwing pairs. This was caused by adverse weather and food scarcity, not by predation (Table 4). The present reproduction figures of Lapwing and Oystercatcher are insufficient to maintain stable population levels, as apparent by a steady decline in Lapwing numbers. Low survival rates are presently caused by high chick mortality, although the majority of nests would have failed anyway without nest protection.