As the tide ebbs, the mudflats of the Wash Estuary provide an enormous feeding table for wading birds; and then as the tide floods the flocks are progressively flushed inland. Over the high tide period the mudflats are completely covered by the sea and the birds fly inland to roost on shore. Snettisham beach in Norfolk is a favourite location for the roost. Hundreds of thousands of wading birds such as knots, oystercatchers, godwits and avocets take to the air in great swirling clouds before swooping en masse low over the shore to settle in the fresh water lagoons alongside the beach. Tens of thousands of knots roost together. The roost attracts raptors such as peregrines and harriers which cause the knots to lift-off in unison forming a wall of wings and a crescendo of calls. The sights and sounds are spectacular.