# Sternula

Sternula is a genus of small white terns, with a global distribution along sheltered sandy coasts and large rivers.
The seven species are all closely related, with similar plumage and size, all are between 22–28 cm long and 39–63 g weight. All are pale grey above, and white or very pale grey below; in all the outer primaries are darker grey (to nearly blackish), but the number of primaries that are dark varies slightly between the species. Most have a distinctive head pattern in the breeding season, with a black crown and eyeline, and a white forehead; one (fairy tern) differs in lacking the black eye line, and one (Damara tern) has a fully black crown with no white forehead in the breeding season. The legs and bill are mostly yellow (with or without a black tip) in the breeding season, but black in Damara tern. In all species the winter plumage has a more extensive white forehead, the bill is black, and the legs darker red-brown to blackish.
Although the genus was first described in 1822 by Friedrich Boie, the species in the genus were generally retained within the larger genus Sterna, the genus that holds most terns, until a study in 2005 showed that this treatment was paraphyletic, with these seven species less closely related to typical Sterna terns, than several other terns long treated in other genera like Chlidonias and Larosterna.
Sternula diverged early from other terns about 16 million years ago, with only the very different noddies (Anous and Gygis), and the 'brown-backed' Onychoprion terns diverging earlier. Despite the early origin of the genus, the current diversity within the genus is much more recent, with the species having a common ancestor around 4 million years ago. Saunders's and least terns were both formerly considered to be subspecies of little tern.
The genus name is a diminutive of Sterna, "tern".

## Species

Seven species are accepted by the IOC World Bird List:
Genus Sternula – F. Boie, 1822 – seven species :
| Common name | Scientific name and subspecies | Range | Size and ecology | IUCN status and estimated population |
| Little tern | Sternula albifrons (Pallas, 1764) Four subspecies S. a. albifrons – (Pallas, 1764) S. a. guineae – (Bannerman, 1931) S. a. placens – Gould, 1871 S. a. sinensis – (J. F. Gmelin, 1789) | temperate and tropical Europe, Africa, Asia, and Australia. | Size: Habitat: Diet: | LC |
| Saunders's tern | Sternula saundersi (Hume, 1877) | north-western Indian Ocean | Size: Habitat: Diet: | LC |
| Least tern | Sternula antillarum Lesson, 1847 Three subspecies S. a. athalassos – (Burleigh & Lowery, 1942) S. a. antillarum – (Lesson, 1847) S. a. browni – (Mearns, 1916) | North America and locally in northern South America. | Size: Habitat: Diet: | LC |
| Yellow-billed tern | Sternula superciliaris (Vieillot, 1819) | Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, Uruguay, and Venezuela. | Size: Habitat: Diet: | LC |
| Peruvian tern | Sternula lorata (Philippi & Landbeck, 1861) | Chile, Ecuador, and Peru | Size: Habitat: Diet: | EN |
| Fairy tern | Sternula nereis (Gould, 1843) Three subspecies Sternula nereis nereis (Gould, 1843) Sternula nereis exsul (Mathews, 1912) Sternula nereis davisae (Mathews & Iredale, 1913) | Australia, New Caledonia,northern New Zealand | Size: Habitat: Diet: | VU |
| Damara tern | Sternula balaenarum Strickland, 1853 | southern Africa and migrates to tropical African coasts | Size: Habitat: Diet: | VU |