Winter population estimates for selected waterfowl species in Britain Original Research Article

British estimates for 42 waterfowl populations have been revised using Wetland Bird Survey data and other published sources covering the 1986/87 to 1991/92 period. These estimates can be used to generate new 1% qualifying levels for assessments of the national significance of wetland sites for waterfowl. Three methods are explored, including extrapolations from the counted to the total population size on the basis of enhanced regional coverage. The suitability of the methods is discussed together with the apparent changes in the population sizes of particular species. British populations are placed in a wider international context, and the importance of sites for total waterfowl assemblages, as summer and moulting locations, and as refuges from severe weather and disturbance is highlighted. It is suggested that it is now important to develop more sophisticated site assessment criteria to allow consideration of these, and other, important aspects of waterfowl use of wetland sites.