There are two species of birds known as turnstones in honour of their ability to turn stones over to find food hidden underneath: the Ruddy Turnstone (Arenaria interpres) and the Black Turnstone (Arenaria melanocephala).

Ruddy Turnstones can be found around the world, but only in coastal areas. Their range stretches as far north as Greenland and northern Canada and as far south as Australia and South Africa. Black Turnstones, on the other hand, are found only on the west coast of North America. Both species breed around the Arctic Circle and migrate south for the winter.

In winter, the two species look somewhat similar, with white underparts and dark brown backs and heads, although the Black Turnstone has a larger dark brown bib than its cousin. In summer, however, the two species are easy to distinguish - as their names suggest, the Black Turnstone develops almost-black plumage on its back while the Ruddy Turnstone develops ruddy red-brown plumage on its back.

In the breeding season, the female turnstone lays up to four eggs in a nest consisting of a scrape lined with grasses. Male and female turnstones take turns to incubate the eggs. The eggs hatch after about three weeks, and the chicks can feed themselves. The chicks are looked after by both parents for about two weeks, then the male looks after them until they learn to fly when they are three to four weeks old. The oldest Black Turnstone known to the Cornell Lab of Ornithology was eight years old. The oldest Ruddy Turnstone known to the Royal Society for the Protection of Birds (RSPB) was 22 years old.

Both species are known for turning over stones, seaweeds and other items of flotsam and jetsam in their coastal habitats. They do this to find food such as worms, crabs and shellfish (and they will also eat carrion such as dead fish). Their beaks are chisel-like and well adapted to prying open their prey as well as to hunting on beaches. In the breeding season in the Arctic, their diet mostly consists of flies and midges, insect larvae and spiders.

The population of Black Turnstones is stable and there are estimated to be around 95,000 adult birds in the wild, so they have been classed as of Least Concern on the International Union for Conservation of Nature’s Red List. The population of Ruddy Turnstones has decreased slightly in recent years, but there are still more than 300,000 adult birds in the wild, so they have also been classed as of Least Concern. They are at risk of predation by animals such as mink, and are also vulnerable to water pollution and disruptions to their food supplies. They are not specially protected in law, but often find sanctuary in conservation areas. In the UK, for example, Ruddy Turnstones can regularly be seen at coastal nature reserves, including Titchfield Haven on the south coast and the North Wirral Coastal Park in the north west.