The ecology of the Wash. 1. Distribution and diet of wading birds (Charadrii).
1. Diet and the main feeding areas of wading birds on the Wash were surveyed during August to May in 1972-73 and 1973-74. The most important species of prey for oystercatchers (Haematopus ostralegus) were Cerastoderma edule and Mytilus edulis; for knots (Calidris canutus) they were Macoma balthica and C. edule; for dunlins (Calidris alpina) they were Hydrobia ulvae and Nereis diversicolor; for redshanks (Tringa totanus) Carcinus maenas, Crangon spp., H. ulvae, N. diversicolor and different amphipods; for curlews (Numenius arquata) they were C. maenas, Lanice conchilega and several other polychaetes and bivalve molluscs; for bar-tailed godwits (Limosa lapponica) L. conchilega, N. diversicolor and M. balthica; for grey plovers (Pluvialis squatarola) L. conchilega, other polychaetes, Cerastoderma, C. maenas and M. balthica. The diet of turnstones (Arenaria interpres), ringed plovers (Charadrius hiaticula) and sanderling (Crocethia alba) were not studied in detail. In general, the larger waders took the larger individuals of prey species and the smaller waders took smaller prey items. The main feeding areas of oystercatchers, knots, dunlins and bar-tailed godwits coincided with the areas where the density of their main prey was highest. This was also the case for redshanks, curlews and grey plovers except that there seemed to be some areas of high density of prey which were little used. Examples are given of the numbers of each species of wader whose feeding areas would be removed by various proposals to build a reservoir in the south-east corner of the Wash. The effect was variable between wader species and alternative schemes, but particularly large numbers of knots and dunlins could be affected.