Turnstones are the bird species in the genus Arenaria in the family Scolopacidae. They are closely related to calidrid sandpipers and might be considered members of the tribe Calidriini.^[1]

Both birds are distinctive medium-sized waders. They are high Arctic breeders, and are migratory. These chunky powerful birds have strong necks and bills well suited to their feeding technique. As the name implies, these species readily turn stones or seaweed looking for hidden invertebrates. They are strictly coastal, preferring stony beaches to sand, and are often found with other waders such as Purple Sandpipers.

Their appearance is striking in flight, with white patches on the back, wings and tail.

Ruddy Turnstone in breeding plumage.

Black Turnstone in summer plumage.

The Ruddy Turnstone (or just Turnstone in Europe), Arenaria interpres, has a circumpolar distribution, and is a very long distance migrant, wintering on coasts as far south as South Africa and Australia. It is thus a common sight on coasts almost everywhere in the world.

In breeding plumage, this is a showy bird, with a black-and-white head, chestnut back, white underparts and red legs. The drabber winter plumage is basically brown above and white below.

This is a generally tame bird and is an opportunist feeder. Unlike most waders, it will scavenge, and has a phenomenal list of recorded food items, including human corpses and coconut.

The call is a staccato tuck- tuck- tuck.

The Ruddy Turnstone is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.

The Black Turnstone (Arenaria melanocephala) has a similar structure to its widespread relative, but has black upperparts and chest, and white below. It has a much more restricted range than the Ruddy Turnstone, breeding in western Alaska, and wintering mainly on the Pacific coast of the USA.

There exists a fossil bone, a distal piece of tarsometatarsus found in the Edson Beds of Sherman County, Kansas. Dating from the mid-Blancan some 4-3 million years ago, it appears to be from a calidriid somewhat similar to a Pectoral Sandpiper, but has some traits reminiscent of turnstones.^[2] Depending on which traits are apomorphic and plesiomorphic, it may be an ancestral representative of either lineage.

Footnotes

References

• Thomas, Gavin H.; Wills, Matthew A. & Székely, Tamás (2004): A supertree approach to shorebird phylogeny. BMC Evol. Biol. 4: 28. doi:10.1186/1471-2148-4-28 PMID 15329156 PDF fulltext Supplementary Material
• Wetmore, Alexander (1937): The Eared Grebe and other Birds from the Pliocene of Kansas. Condor 39(1): 40. PDF fulltext DjVu fulltext