(1) Trends in the numbers of grey plovers wintering on forty-five British estuaries in 1970-86 were examined from the results of an estuary bird counting programme. (2) An index of the numbers of grey plovers wintering in Britain approximately tripled over this period. Historical counts from four estuaries in southern England suggest that this population increase has been continuing since at least the 1930s. (3) There were large differences in the rates of change in numbers on individual estuaries: on some, numbers increased faster than the national population, whilst on others there was a smaller, or even no, increase. These patterns indicated that sites were being filled sequentially, allowing each estuary to be classified according to its preference by grey plovers. (4) The rates at which grey plovers increased on an estuary was significantly negatively correlated with their initial density. There was a limit to the numbers wintering on each estuary, which could be described as the carrying capacity of that estuary for grey plovers. (5) By the winter of 1985-86, almost 50% of the estuaries examined were at, or approaching, their carrying capacity for grey plovers. Implications for the conservation of wader populations are discussed.