''Onychoprion'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of four species of

tern Terns are seabirds in the family Laridae, subfamily Sterninae, that have a worldwide distribution and are normally found near the sea, rivers, or wetlands. Terns are treated in eleven genera in a subgroup of the family Laridae, which also ...

s in the family Laridae. The genus name is from

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

, "claw" or "nail", and , "saw". As a group, they have been variously called "brown-winged terns" or "brown-backed terns", though only one species is actually brown; the other three are dark grey or black.

Species

Although the genus ''Onychoprion'' was first described in 1832 by

Johann Georg Wagler Johann Georg Wagler (28 March 1800 – 23 August 1832) was a German herpetologist and ornithologist. Wagler was assistant to Johann Baptist von Spix, and gave lectures in zoology at the Ludwig Maximilian University of Munich after it was moved t ...

, 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 Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

, with these four species less closely related to typical ''Sterna'' terns, than several other terns long treated in other genera like '' Chlidonias'' and '' Larosterna''.Bridge, E. S.; Jones, A. W. & Baker, A. J. (2005)
A phylogenetic framework for the terns (Sternini) inferred from mtDNA sequences: implications for taxonomy and plumage evolution
. ''Molecular Phylogenetics and Evolution'' 35: 459–469. ''Onychoprion'' diverged early from other terns about 16–18 million years ago, with only the very different noddies (''Anous'' and ''Gygis'') diverging earlier. Within the genus, Aleutian tern is the most divergent, splitting off from the rest about ten million years ago; then sooty tern diverged about seven to eight million years ago, and finally bridled and spectacled terns diverged from each other about three million years ago. Three of the four species are

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

, and one has a sub-polar breeding range. The sooty tern has a pan-tropical distribution; the bridled tern also breeds across the Tropical

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

and

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

but in the central

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the cont ...

it is replaced by the

spectacled tern The spectacled tern (''Onychoprion lunatus''), also known as the grey-backed tern, is a seabird in the family Laridae. Description A close relative of the bridled and sooty terns (with which it is sometimes confused), the spectacled tern is l ...

. The Aleutian tern breeds around

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

and

Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...

but winters in the tropics around

South East Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

Cultural aspects

''Manutara'' is the Rapa Nui language name for spectacled and sooty terns. Both arrive at

Easter Island Easter Island (, ; , ) is an island and special territory of Chile in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian Triangle in Oceania. The island is renowned for its nearly 1,000 extant monumental statues, ...

and hatch their eggs on the island called

Motu Nui Motu Nui is the largest of the Islet, islets located off the southwestern coast of Easter Island (Rapa Nui) and constitutes the westernmost point of Chile. Covering an area of 3.9 hectares, it is the summit of a submerged volcanic mountain tha ...

, an event that was used for an annual rite called Tangata manu.

References

{{Taxonbar, from=Q1088377 Bird genera Terns