Adults have short dark legs and a medium thin dark bill. The body is mottled grey on top with cinnamon face, throat and breast and light-coloured rear belly. In winter the plumage becomes uniformly pale grey.
They migrate to coastal areas on the Atlantic and Pacific coasts in winter, as far south as Argentina. Old World birds migrate to the Mediterranean, the British Isles, Africa and Australasia. This species forms enormous flocks in winter.
These birds forage on mudflats and beaches, probing or picking up food by sight. They mainly eat mollusks and insects, also plant material.
Near the end of the 19th century, large numbers were shot for food during migration in North America.
It is sometimes said that this bird gets its name from King Cnut, but there is no factual basis for this story.