De Scholekster Haematopus ostralegus als broedvogel van Assen en omstreken

In 2008 Oystercatcher territories were mapped in a 2729 ha area in the eastern part of the city of Assen and the adjacent fields and meadows (Fig. 1). The species preferred to breed in the industrial areas of the city where they nest on fiat roofs and in fields. Meadows and densely built up (and populated) areas were generally avoided. Densities ranged from 1.1 pairs/100 ha in agricultural landscapes to 13.3 pairs/100 ha (Table 1). In general densities in the industrial city areas were five times higher than in agricultural areas. During the last 20 years the species almost disappeared from meadow reserves and decreased in most agricultural areas (table 2). No old counts are available from the built up area, but probably numbers are stable there or even slightly increased during the last decades. In the built up areas territories were occupied earlier than in farmland (Fig.2). Hatching and fledging success turned out to be very low in farmland (Table 4 and 5) and considerably higher (but still low) in urban Oystercatchers. Differences are explained by higher predation risk ofdutches in agricultural area andprobably better food conditions on the lawns in the built up area.