The UK's estuaries are internationally important for wintering waterfowl and yet these habitats are subject to a range of pressures. For example, some 88% of them have been affected by landclaim. This stress to estuaries will be compounded by global climate change, which will lead to sea level rise. It would be valuable, therefore, to be able to predict the likely impact of such pressures on waterfowl using estuaries. This paper presents a method, based on environmental variables that can easily be collected, which allows the effect of habitat change on densities of wintering waterfowl to be predicted for individual estuaries. The application of the methodology is demonstrated in detail for Redshank. Waterfowl counts were carried out two hours either side of low tide over two winters at 27 estuarine sites in Britain. The sediment classification was obtained from the interpretation of airborne or satellite thematic imagery. The morphology of each site was measured largely from maps. A combination of estuary length, estuary width, tidal range and longitude describe 87% of the variance in the whole estuary Redshank densities. A model based on sediment, the proportion of mud in estuaries, explained 48% of the variance. The suspected reasons behind the higher predictive potential of the former model are discussed. Two examples of the use of these models in predicting the likely effects of human developments on waterfowl populations are demonstrated. Further development of the models is suggested which would allow them to be applied to an important conservation issue, global climate change.
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