Onychoprion, the "brown-backed terns", is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of seabird

Seabird

Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...

s in the tern

Tern

Terns are seabirds in the family Sternidae, previously considered a subfamily of the gull family Laridae . They form a lineage with the gulls and skimmers which in turn is related to skuas and auks...

 family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

. Although the genus was first described in 1832 by Johann Georg Wagler

Johann Georg Wagler

Johann Georg Wagler was a German herpetologist.Wagler was assistant to Johann Baptist von Spix, and became Director of the Zoological Museum at the University of Munich after Spix's death in 1826...

 the four species in the genus were until recently retained in the larger genus Sterna

Sterna

Sterna is a genus of terns in the bird family Sternidae. It used to encompass most "white" terns indiscriminately, but mtDNA sequence comparisons have recently determined that this arrangement is paraphyletic...

, the genus that most terns are in (Bridge et al., 2005).

Three of the four species are tropical

Tropics

The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately  N and the Tropic of Capricorn in the southern hemisphere at  S; these latitudes correspond to the axial tilt of the Earth...

, and one has a sub-polar breeding range. The Sooty Tern

Sooty Tern

The Sooty Tern, Onychoprion fuscatus , is a seabird of the tern family . It is a bird of the tropical oceans, breeding on islands throughout the equatorial zone. Colloquially, it is known as the Wideawake Tern or just wideawake...

 has a pan-tropical distribution; the Bridled Tern

Bridled Tern

The Bridled Tern is a seabird of the tern family Sternidae. It is a bird of the tropical oceans.-Description:...

 also breeds across the Tropical Atlantic and Indian Ocean

Indian Ocean

The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...

 but in the central Pacific it is replaced by the Spectacled Tern. The Aleutian Tern

Aleutian Tern

The Aleutian Tern is a seabird of the tern family Sternidae....

 breeds around Alaska

Alaska

Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...

 and Siberia

Siberia

Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...

 but winters in the tropics around South East Asia.

• Genus Onychoprion – "brown-backed" terns.
  • Spectacled Tern, Onychoprion lunatus
  • Bridled Tern
    Bridled Tern
    The Bridled Tern is a seabird of the tern family Sternidae. It is a bird of the tropical oceans.-Description:...
    
    , Onychoprion anaethetus
  • Sooty Tern
    Sooty Tern
    The Sooty Tern, Onychoprion fuscatus , is a seabird of the tern family . It is a bird of the tropical oceans, breeding on islands throughout the equatorial zone. Colloquially, it is known as the Wideawake Tern or just wideawake...
    
    , Onychoprion fuscatus
  • Aleutian Tern
    Aleutian Tern
    The Aleutian Tern is a seabird of the tern family Sternidae....
    
    , Onychoprion aleuticus

Manutara is the Rapa Nui language

Rapa Nui language

Rapa Nui , also known as Pascuan or Pascuense, is an Eastern Polynesian language spoken on the island of Rapa Nui, also known as Easter Island....

 name for Spectacled and Sooty Terns. Both arrive at Easter Island

Easter Island

Easter Island is a Polynesian island in the southeastern Pacific Ocean, at the southeasternmost point of the Polynesian triangle. A special territory of Chile that was annexed in 1888, Easter Island is famous for its 887 extant monumental statues, called moai, created by the early Rapanui people...

 and hatch their eggs on the island called Motu Nui

Motu Nui

Motu Nui is the largest of three islets just south of Easter Island and is the most westerly place in Chile. All three islets have sea birds but Motu Nui was also an essential location for the Tangata manu cult which was the island religion between the moai era and the Christian times...

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

Tangata manu

The Tangata manu , was the winner of a traditional competition on Rapa Nui . The ritual was an annual competition to collect the first Sooty Tern egg of the season from the islet of Motu Nui, swim back to Rapa Nui and climb the sea cliff of Rano Kau to the clifftop village of Orongo.-Myth:In the...

.