Declines in midwinter counts of waders roosting on the Dee estuary

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Abstract
A 57% decline in the total number of waders counted roosting on the Dee estuary between 1975/76 and 1984/85 can largely be explained by declines in 3 species. Numbers of Bar-tailed Godwit have declined by 99% from a peak of 11149 in 1976/77 to 25 birds in 1984/85; Knots have declined by 79% from a peak count of 48 000 in 1979/80 to 10150 in 1985/86; and Dunlins have declined by 81% from a peak of 46826 in 1975/76 to 8800 in 1985/86. National populations of Knot and Dunlin have also declined but the trend on the Dee has been more pronounced. In contrast, the number of Bar-tailed Godwits wintering in Britain has increased during the period of decline on the Dee. Counts elsewhere, supported by observations of flock movements, suggest that Bar-tailed Godwits and Knots that formerly roosted on the Dee have switched to roosting on the Alt estuary. For some Knots at least, this incurs an extra 40 km round-trip flight between feeding grounds and roosts on each tidal cycle, which may account for 14% of their daily energy expenditure. The change is probably a consequence of increased levels of disturbance on the outer Dee roost sites, particularly from dogs, horseriders and walkers.