A very contrasting wader which looks like a large House Martin in flight. Its dark, almost black upperparts, pale underparts and white rump are distinctive. It frequently bobs up and down when standing. It often appears nervous and will fly off with a low zig-zagging flight when disturbed.

Look for migrant birds near almost any freshwater margins - marshes, lakes, gravel pits and rivers. In winter it likes sewage works, watercress beds and freshwater marshes.

Seen in the UK mostly between July and March.

Feeds on insects.

Largely confined to England and Wales. The UK has a wintering population of 500 to 1,000 birds.

Fairly common on passage, with groups of fifteen or more, in Leicestershire and Rutland.