Grey-backed Tern
Encyclopedia
The Spectacled Tern also known as the Grey-backed Tern, is a seabird
in the tern
family
.
and Sooty Tern
s (with which it is sometimes confused), the Spectacled Tern is less common than the other members of its genus
and is has been studied less. The three species, along with the Aleutian Tern
were recently split into a new genus Onychoprion from Sterna
(Bridge et al., 2005). They resemble the Sooty Tern but with a grey back instead of a black one. Their breast and underparts are white, and the have a black eye line from the bill to the back of the head.
. At the northern end of its distribution it nests in the Northwestern Hawaiian Islands
(with the largest population being Lisianski Island
) and two small islets off Oahu
, in the east as far as the Tuamotu Islands, with other colonies in the Society Islands
, the Line Islands
, Phoenix Islands
, Mariana Islands
and American Samoa
. There are unconfirmed reports of breeding as far south as Fiji
, and as far east as Easter Island
. Little is known about the populations outside of Hawaii. Outside of the breeding season the species is partly migratory
, with birds from the Hawaiian Islands flying south. It is thought that birds in other parts of the Pacific are also migratory, and will disperse as far as Papua New Guinea
, the Philippines, and Easter Island
.
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...
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...
.
Description
A close relative of the BridledBridled Tern
The Bridled Tern is a seabird of the tern family Sternidae. It is a bird of the tropical oceans.-Description:...
and 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...
s (with which it is sometimes confused), the Spectacled Tern is less common than the other members of its 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...
and is has been studied less. The three species, along with the Aleutian Tern
Aleutian Tern
The Aleutian Tern is a seabird of the tern family Sternidae....
were recently split into a new genus Onychoprion from 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...
(Bridge et al., 2005). They resemble the Sooty Tern but with a grey back instead of a black one. Their breast and underparts are white, and the have a black eye line from the bill to the back of the head.
Distribution and habitat
The Spectacled Tern breeds on islands of the tropical Pacific OceanPacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. At the northern end of its distribution it nests in the Northwestern Hawaiian Islands
Northwestern Hawaiian Islands
The Northwestern Hawaiian Islands or the Leeward Islands are the small islands and atolls in the Hawaiian island chain located northwest of the islands of Kauai and Niihau. They are administered by the U.S. state of Hawaii except Midway Atoll, which has temporary residential facilities and is...
(with the largest population being Lisianski Island
Lisianski Island
Lisianski Island is one of the Northwestern Hawaiian Islands, with a land area of and a maximum elevation of above sea level. Honolulu is away, to the southeast. Linked to Lisianski are the extensive Neva Shoals...
) and two small islets off Oahu
Oahu
Oahu or Oahu , known as "The Gathering Place", is the third largest of the Hawaiian Islands and most populous of the islands in the U.S. state of Hawaii. The state capital Honolulu is located on the southeast coast...
, in the east as far as the Tuamotu Islands, with other colonies in the Society Islands
Society Islands
The Society Islands are a group of islands in the South Pacific Ocean. They are politically part of French Polynesia. The archipelago is generally believed to have been named by Captain James Cook in honor of the Royal Society, the sponsor of the first British scientific survey of the islands;...
, the Line Islands
Line Islands
The Line Islands, Teraina Islands or Equatorial Islands, is a chain of eleven atolls and low coral islands in the central Pacific Ocean, south of the Hawaiian Islands, that stretches for 2,350 km in a northwest-southeast direction, making it one of the longest islands chains of the world...
, Phoenix Islands
Phoenix Islands
The Phoenix Islands are a group of eight atolls and two submerged coral reefs, lying in the central Pacific Ocean east of the Gilbert Islands and west of the Line Islands. They are a part of the Republic of Kiribati. During the late 1930s they became the site of the last attempted colonial...
, Mariana Islands
Mariana Islands
The Mariana Islands are an arc-shaped archipelago made up by the summits of 15 volcanic mountains in the north-western Pacific Ocean between the 12th and 21st parallels north and along the 145th meridian east...
and American Samoa
American Samoa
American Samoa is an unincorporated territory of the United States located in the South Pacific Ocean, southeast of the sovereign state of Samoa...
. There are unconfirmed reports of breeding as far south as Fiji
Fiji
Fiji , officially the Republic of Fiji , is an island nation in Melanesia in the South Pacific Ocean about northeast of New Zealand's North Island...
, and as far east as 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...
. Little is known about the populations outside of Hawaii. Outside of the breeding season the species is partly migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
, with birds from the Hawaiian Islands flying south. It is thought that birds in other parts of the Pacific are also migratory, and will disperse as far as Papua New Guinea
Papua New Guinea
Papua New Guinea , officially the Independent State of Papua New Guinea, is a country in Oceania, occupying the eastern half of the island of New Guinea and numerous offshore islands...
, the Philippines, and 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...
.