Population estimates for waders Charadrii wintering in Great Britain, 1987/88-1991/92

Britain's wintering wader populations were estimated for the period 1987/88-1991/92 from data provided from three sources: the Wetland Bird Survey (WeBS), the Winter Shorebird Count and the Winter Atlas. WeBS is the annual monitoring scheme for non-breeding water-fowl populations in the United Kingdom. It achieves excellent coverage of the important concentrations of waders living within estuaries, but the coverage of populations using non-estuarine coasts and inland habitats is incomplete. The Winter Shorebird Count, conducted in 1984/85, was a comprehensive survey of waders wintering on non-estuarine coasts while the Winter Atlas provides distributional data for all bird species in Britain and ireland for three winters in the early 1980s and is a source of information on inland wader populations. The wader populations on non-estuarine coasts were estimated from sites counted in both 1984/85 and in 1987/88-1991/92 as part of WeBS, enabling calibration of the Winter Shorebird Count data. The results suggest that Britain's coastline supports approximately 1-65 million waders. Values are presented from which site evaluations based on 1% of the national population can be derived. Comparison of the new coastal population estimates with the previous estimates (for the period 1981-85) suggests that numbers of most species of wintering waders have increased on estuaries and non-estuarine coasts during the last decade. These population changes are compared with trends in British wintering wader populations as shown by application of a model-based method of indexing populations. The possible causes of between-year fluctuations in wader populations are discussed and the importance of long-term monitoring schemes emphasised. Copyright (C) 1996 Elsevier Science Ltd