The ruddy turnstone (Arenaria interpres) is a small cosmopolitan wading bird, one of two species of turnstone in the genus Arenaria.
It is now classified in the sandpiper family Scolopacidae but was formerly sometimes placed in the plover family Charadriidae. It is a highly migratory bird, breeding in northern parts of Eurasia and North America, and flying south to winter on coastlines almost worldwide. It is the only species of turnstone in much of its range and is often known simply as turnstone.
In Africa, it is common all the way down to South Africa with good numbers on many offshore islands. In Asia, it is widespread in the south with birds wintering as far north as southern China and Japan (mainly in the Ryukyu Islands). It occurs south to Tasmania and New Zealand and is present on many Pacific islands. Some non-breeding birds remain year round in many parts of the wintering range, with some of those birds still taking on breeding plumage in the spring and summer.
The ruddy turnstone has a varied diet including carrion, eggs, fish and plant material but it feeds mainly on invertebrates. Insects and their larvae are particularly important in the breeding season. At other times it also takes crustaceans, spiders, molluscs, and worms. It often flips over stones and other objects to get at prey items hiding underneath; this behaviour is the origin of the name "turnstone". It usually forages in flocks.
They have also been observed preying on the eggs of other bird species such as gulls, terns, ducks, and even other turnstones, though this behaviour is uncommon. In the majority of observed cases, turnstones typically go after undefended or unattended nests, puncturing the shells with their beaks to get at the contents within.
