Thousands of wading birds flocking onto dry sandbanks during the month's highest tide at The Wash estuary in Norfolk, Britain, yesterday.

Square-sided The Wash, among the largest estuaries in Britain, is a giant tidal basin enclosing more than 260 sq km of salt marsh, sand shoals and mud banks.

A sea wall in the estuary has been breached in three places to increase the salt-marsh area to provide an extra habitat for birds, particularly waders, and also to act as a natural flood prevention measure.

The region, which has been designated a Special Protection Area under a European Union directive on the conservation of wild birds, is also where common seals breed and hundreds of thousands of geese and ducks spend their winter.