ENS BJ, WINTERMANS GJM & SMIT CJ (1993) Distribution of wintering waders in the Dutch Wadden Sea. LIMOSA 66 (4): 137-144.

This paper reports the preliminary results of an analysis that ultimately seeks to identify the major habitat variables determining the distribution patterns of different wader species along the East-Atlantic Flyway. Counts made in winter (Nov.-Feb.) between 1966 and 1984 in the Dutch Wadden Sea (split up into 15 counting areas, fig. I) were combined with information on the substrate of feeding areas derived from a habitat map (Dijkema et al. 1989). For practical reasons, no more than five substratetypes were distinguished: sandy areas with a long emersion time, sandy areas with a short emersion time, muddy areas with a long emersion time, muddy areas with a short emersion time, and musselbeds (tab. I). Only large-sized wader species are common in the Dutch Wadden Sea in winter (tab. 2). The total number of waders was positively correlated with the total surface of intertidal mudflats (fig. 2). For most species, the surface of a specific substrate- type correlated more strongly with their wintering numbers than did the total surface of intertidal mudflat (tab. 3). When more than one substrate correlated significantly with the wintering numbers of a species a multiple regression was used to find the most important substrate. Next, a regression through the origin allowed the estimation of densities in which the various wader species are expected to occur in their preferred habitats (tab. 4). The rationale for this procedure is the idea that the total intertidal area can be thought of as a mosaic of different substrates, where different bird species occur in different densities (fig. 3). The results are in general agreement with other reports on the habitat preferences ofthe investigated bird species. It is hoped that the paper will stimulate local groups to analyse and publish their counting data. Ruddy Turnstone Arenaria interpres Dunlin Calidris alpina = Calidris alpina schinzii Red Knot Calidris canutus Eurasian Oystercatcher Haematopus ostralegus Bar-tailed Godwit Limosa lapponica Eurasian Curlew Numenius arquata Grey Plover Pluvialis squatarola Pied Avocet Recurvirostra avosetta Common Redshank Tringa totanus

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