TOWARDS PREDICTING THE EFFECT OF SALT-MARSH RECLAMATION ON FEEDING BIRD NUMBERS ON THE WASH

1. The intertidal feeding grounds of shelduck Tadorna tadorna and seven wader species (Charadrii) on the Wash were censused in 1985-87 to determine the numbers of birds whose downshore feeding grounds would be affected by a narrowing of the shore through further salt-marsh reclamation. 2. Bird distribution was reasonably constant over time, both between seasons within years and between years when 1985-87 was compared with 1972-74. In general, larger numbers of birds fed on wide shores than narrow ones, the species concerned depending on the area of either mud or sand present. 3. Satellite image analysis of the surface sediments showed that shores less than 1.5 km wide (marsh edge to Low Water Mark) were almost entirely muddy whereas wider shores (maximum width of 5 km) were either predominantly sandy or muddy, depending on their position around the Wash. 4. A simple model related the numbers of each species feeding downshore of the marsh in a standardized 1-km wide transect to the area of either sand or mud present, and thus to the width of the shore itself. It was concluded that the model provided a basis for predicting the numbers of birds whose feeding area would be affected by a marsh reclamation of any-given distance down the shore. However, further extensive data collection and model testing are required before this can be done.