Numbers of wintering waders on the North Sea coast of the Netherlands in January 1998

This paper provides estimates of the total number of waders wintering along the Dutch North Sea coast in January 1998, counted as part of the European Non-Estuarine Coastal Waterbird Survey (Europe-NEWS). Although there have been annual midwinter counts of waterbirds along the Dutch North Sea coast since 1993, comprehensive coverage had not previously been attained prior to January 1997. In January 1998 an extra effort was made to count waterbirds along the coast as completely as possible. The Dutch North Sea coast (365 km) consists mainly of sandy beaches, interspersed with breakwaters, dikes and harbours. In total 97% of the coastline was counted in 1998. A simple model was used to estimate numbers for those sites not counted. Waders that only used beaches for roosting at high tide were subtracted from the grand total. In January 1998, Eurasian Oystercatcher Haematopus ostralegus (6,347 birds), Sanderling Calidris alba (3,629) and Ruddy Turnstone Arenaria interpres (1,210) were the dominant wader species. Compared to the total numbers of these species in the Netherlands, 2.5%, 79.3% and 38% respectively wintered along the Dutch non-estuarine North Sea coast. Purple Sandpiper Calidris maritima (205 birds) wintered only on the non-estuarine North Sea coast. January 1998 was a mild winter and the wader totals were comparable to those of other recent mild winters (e.g. between January 1999 and January 2001). The North Sea coast is more important for waders in severe winters, when there may be influxes of birds from other countries and / or redistribution within the country itself. In the severe weather of January 1997 for instance, both the absolute numbers and the percentages of species wintering along the open coast increased. In the mild winter of 1997/98 an estimated 0.6 %, 3.0%, 0.3% and 0.8% of the respective biogeographic populations of Eurasian Oystercatcher, Sanderling, Purple Sandpiper and Ruddy Turnstone overwintered along the Dutch North Sea coast. In the severe winter of 1996/97 these figures increased to 1.1%, 4.8%, 0.5% and 1.9% respectively.