Knots (Calidris canutus) in water. This stocky shorebird is commonly spotted feeding in estuaries around the coast. Knots are highly migratory birds that breeds in the high Arctic and winters in coastal areas of Europe, Africa, and South America. They can travel up to 15,000 kilometres, stopping along the way at least once to feed on invertebrates and molluscs and crustaceans buried in the mud.