The Antarctic tern (''Sterna vittata'') is a seabird in the family

Laridae Laridae is a family of seabirds in the order Charadriiformes that includes the gulls, terns, skimmers and kittiwakes. It includes around 100 species arranged into 22 genera. They are an adaptable group of mostly aerial birds found worldwide. ...

. It ranges throughout the southern oceans and is found on small islands around Antarctica as well as on the shores of the mainland. Its diet consists primarily of small fish and crustaceans. It is very similar in appearance to the closely related

Arctic tern The Arctic tern (''Sterna paradisaea'') is a tern in the family (biology), family Laridae. This bird has a :wiktionary:circumpolar, circumpolar breeding distribution covering the Arctic and sub-Arctic regions of Europe (as far south as Brittan ...

, but it is stockier, and it is in its breeding

plumage Plumage ( "feather") is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, ...

in the southern summer, when the Arctic tern has shed old feathers to get its non-breeding plumage. The Antarctic tern does not migrate like the Arctic tern does, but it can still be found on a very large range. This tern species is actually more closely related to the

South American tern The South American tern (''Sterna hirundinacea'') is a species of tern found in coastal regions of southern South America, including the Falkland Islands, ranging north to Peru (Pacific coast) and Brazil ( Atlantic coast). It is generally the mo ...

. Gulls,

skua The skuas are a group of predatory seabirds with seven species forming the genus ''Stercorarius'', the only genus in the family Stercorariidae. The three smaller skuas, the long-tailed skua, the Arctic skua, and the pomarine skua are called ja ...

s and jaegers are the primary predators of the bird's eggs and young. The Antarctic tern can be further divided into six subspecies. The total global population of this bird is around 140,000 individuals.

Taxonomy

The Antarctic tern was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's '' Systema Naturae''. He placed it with the other terns in the genus ''

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

'' and coined the

binomial name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''Sterna vittata''. Gmelin based his description on the "wreathed tern" that had been described in 1785 by the English ornithologist John Latham in his book ''A General Synopsis of Birds ''. Latham had been provided with a specimen by the naturalist

Joseph Banks Sir Joseph Banks, 1st Baronet, (19 June 1820) was an English naturalist, botanist, and patron of the natural sciences. Banks made his name on the 1766 natural-history expedition to Newfoundland and Labrador. He took part in Captain James C ...

. Latham mistakenly believed it had come from

Christmas Island Christmas Island, officially the Territory of Christmas Island, is an states and territories of Australia, Australian external territory comprising the island of the same name. It is located in the Indian Ocean, around south of Java and Su ...

in the Indian Ocean but it had actually been collected at Christmas Harbour in the

Kerguelen Islands The Kerguelen Islands ( or ; in French commonly ' but officially ', ), also known as the Desolation Islands (' in French), are a group of islands in the sub-Antarctic constituting one of the two exposed parts of the Kerguelen Plateau, a lar ...

in December 1776 during James Cook's third voyage to the Pacific Ocean. A drawing of the bird was made by

William Wade Ellis William Wade Ellis (1751 – 1785) was an artist, a naturalist, and a surgeon's mate on Captain James Cook's voyages. His middle name was wrongly identified as Webb in some sources. He is known largely from the paintings of natural history subjects ...

. The genus name ''Sterna'' comes from the Old English word for a black tern. The specific epithet ''vittata'' is from Latin ''vittatus'' meaning "banded". There are six recognized subspecies, each with their specific breeding sites. *''S. v. tristanensis'' Murphy, 1938 – Tristan da Cunha & Gough Island *''S. v. sanctipauli''

Gould Gould may refer to: People * Gould (name), a surname Places United States * Gould, Arkansas, a city * Gould, Colorado, an unincorporated community * Gould, Ohio, an unincorporated community * Gould, Oklahoma, a town * Gould, West Virginia, ...

, 1865 –

St. Paul Paul; grc, Παῦλος, translit=Paulos; cop, ⲡⲁⲩⲗⲟⲥ; hbo, פאולוס השליח (previously called Saul of Tarsus;; ar, بولس الطرسوسي; grc, Σαῦλος Ταρσεύς, Saũlos Tarseús; tr, Tarsuslu Pavlus; ...

& Amsterdam Islands. *''S. v. georgiae'' Reichenow, 1904 –

South Georgia South Georgia ( es, Isla San Pedro) is an island in the South Atlantic Ocean that is part of the British Overseas Territory of South Georgia and the South Sandwich Islands. It lies around east of the Falkland Islands. Stretching in the east� ...

South Orkney The South Orkney Islands are a group of islands in the Southern Ocean, about north-east of the tip of the Antarctic PeninsulaSouth Sandwich Islands *''S. v. gaini'' Murphy, 1938 – South Shetland Islands,

Antarctic Peninsula The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martín in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctic ...

& nearby islands *''S. v. vittata'' Gmelin, 1789 – Prince Edward, Crozet,

Kerguelen The Kerguelen Islands ( or ; in French commonly ' but officially ', ), also known as the Desolation Islands (' in French), are a group of islands in the sub-Antarctic constituting one of the two exposed parts of the Kerguelen Plateau, a la ...

, Bouvet & Heard Islands *''S. v. bethunei'' Buller, 1896 – Stewart, Snares,

Auckland Auckland (pronounced ) ( mi, Tāmaki Makaurau) is a large metropolitan city in the North Island of New Zealand. The most populous urban area in the country and the fifth largest city in Oceania, Auckland has an urban population of about It ...

Bounty Bounty or bounties commonly refers to: * Bounty (reward), an amount of money or other reward offered by an organization for a specific task done with a person or thing Bounty or bounties may also refer to: Geography * Bounty, Saskatchewan, a g ...

Antipodes In geography, the antipode () of any spot on Earth is the point on Earth's surface diametrically opposite to it. A pair of points ''antipodal'' () to each other are situated such that a straight line connecting the two would pass through Ear ...

, Campbell &

Macquarie Macquarie may refer to: People * Lachlan Macquarie, Governor of the British colony of New South Wales from 1810 to 1821. * Elizabeth Macquarie Campbell, Lachlan Macquarie's second wife Locations * Division of Macquarie, an electoral district in th ...

Islands Terns are in the family

along with gulls and skimmers. Terns make up the sub-family Sterninae, which spreads into eleven genera. The Antarctic terns are in the genus

, which has been established to be monophyletic. However, this claim has been challenged by a genetic study.

Description

The Antarctic tern is a medium-sized tern ranging from in length with a wingspan of . It weighs between but it tends to be heavier during the winter months. In breeding plumage, the tern has light grey body and wings. Its deeply forked tail, lower back just above it and cheeks are white. It also has a distinctive black cap that reaches from the nape down to the bill and the eye is brownish-black. The bill, legs and feet are bright red. In non-breeding plumage, the black cap is reduced to just the area behind the eyes, the underparts become lighter and the bill becomes a dull reddish-black colour. Juveniles have yellowish-brown, grey, and white spots on their backs, with a yellowish-brown belly and breast. Their bill is dull black and the legs are dull red. The chicks have a yellowish-brown colour with black spots on their heads and back. They have a greyish white belly with a darker throat. The bill, legs and feet can be flesh colored or reddish black. The Antarctic tern resembles closely to the

. However, the local Antarctic Terns are in their breeding plumage when the migrating Arctic Terns arrive in their non-breeding plumage. Arctic terns also have shorter legs and more prominent black margins on the outside of their primary feathers. The

white-fronted tern The white-fronted tern (''Sterna striata''), also known as tara, sea swallow, black-billed tern, kahawai bird, southern tern, or swallow tail, was first described by Johann Friedrich Gmelin in 1789. A medium-sized tern with an all-white body inclu ...

is also quite similar to the Antarctic tern but it can be distinguished by the larger body size, lighter colors, and longer black bill of the white-fronted tern. The different subspecies vary in size and plumage tone but are often hard to distinguish from one another. Antarctic terns are quite noisy around their roost sites. “trr-trr-kriah” is their main call and is given when they are in flight or fishing. They also use a “chrrrr” to defend their nests against intruders or predators. They make a higher-pitched call to catch the attention of their mates.

Distribution and habitat

The Antarctic tern prefers rocky areas such as islets, with or without vegetation, often among other seabird species. It usually nests on cliffs but is also found on rocky beaches, places inaccessible to cats or rats. It also avoids beaches with sea lions, as they tend to occupy all flat areas. Outside of the breeding season, this species of tern looks for ice edges in Antarctica. It also visits South Africa's beaches and rocky cliffs. This species has a large range, widely distributed around sub-Antarctic islands of the southern hemisphere and the Antarctic mainland. The breeding territory of the Antarctic tern includes the Antarctic continent, Bouvet Island, the French Southern Territories, Saint Helena, Ascension and Tristan da Cunha, South Africa, South Georgia, and the South Sandwich Islands. Recently, some populations have been found to take advantage of newly ice-free terrain on the north-eastern Antarctic Peninsula when nesting. Each subspecies have specific breeding islands. After breeding, the Antarctic tern does not undertake a long migration to the opposite pole like the Arctic tern does. It usually remains close to the breeding islands all year round. However, the more southern populations migrate slightly further north for the rest of the year. They can be found in Uruguay, Argentina, Brazil, Chile, the Falkland Islands, the Heard Island, the McDonald Islands, Australia, and New Zealand.

Behavior and ecology

Food and feeding

The Antarctic tern is an opportunistic feeder that mostly eats small fishes as well as some

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s like

Antarctic krill Antarctic krill (''Euphausia superba'') is a species of krill found in the Antarctic waters of the Southern Ocean. It is a small, swimming crustacean that lives in large schools, called swarms, sometimes reaching densities of 10,000–30,000 ind ...

. It usually fishes gregariously, forming flocks of up to 100 birds when they locate larger shoals. It fishes by hovering a few meters above the sea. When a prey is located, the tern has two strategies: most of the time it will directly plunge dive and become completely submerged but if the water is too rough it will only submerge its bill whilst in flight. It normally forages near the shore in the kelp zone. It has also been found in the intertidal zone, scavenging for small crustaceans,

polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are ma ...

s, and

shellfish Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater enviro ...

. However, during the breeding season, it does not venture very far from its nest.

Breeding

The Antarctic tern usually breeds from November to December, but this can vary depending on climate and the availability of food. The birds are usually found in loose colonies of 5 to 20 pairs, although they may also nest as isolated pairs. However, some islands are home to much larger populations and have colonies of over 1000 pairs. This tern species usually selects depressions or scrapes on the cliff ledge for nesting. It can also be found nesting on the soil, sand, glacial

moraine A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice she ...

s, or a vegetation mat, often within a small pit of pebbles or shells. The female will lay one or two eggs per breeding season, which will be incubated by both parents for a period of 23 to 25 days. Chicks hatch during the summer months, from December to February. Then, the chicks need to be fed by their parents for 27 to 32 days while they grow fully developed flight feathers. Both members of the pair attend their young for several weeks even after this period. Antarctic terns that survive their first year have a life expectancy of about 17 years with an estimated reproductive time span of about 10 years as they can start breeding at 3 years old. Gulls,

s and jaegers feed on the eggs and chicks. The larger water birds also prey upon the adults, leaving young chicks exposed to the harsh weather conditions and starvation. The Antarctic tern will defend its nest against any intruders by repeated dive bombing, occasionally striking them with their sharp bill.

Threats and Conservation

The IUCN Red List classifies the Antarctic tern as a species of least concern in terms of conservation status. The population is stable and is currently estimated to be between 132,000 and 145,000 individuals, with about 45,000 breeding pairs. The majority are from the subspecies S. ''v. gaini.'' However, reproduction failures have been recorded on certain islands mostly due to introduced mammalian predators, namely domestic cats and rats. File:Antarctic tern - Sterna vittata.jpg, Antarctic tern in breeding plumage File:Chick and adult Antarctic tern.jpg, Adult Antarctic tern (front) in breeding plumage with a chick (back). File:Antarctic Tern at Moltke Harbour.jpg, Antarctic tern in flight File:Antarctic tern in flight.jpg, Antarctic tern in flight, seen from below.

References

External links

BirdLife International

Encyclopedia of Life

Birds of the World

Cornell Lab of Ornithology

Antarctic tern conservation - Government of Australia

The Antarctic tern in New Zealand

Species text in The Atlas of Southern African Birds
{{Taxonbar, from=Q509423

Antarctic tern The Antarctic tern (''Sterna vittata'') is a seabird in the family Laridae. It ranges throughout the southern oceans and is found on small islands around Antarctica as well as on the shores of the mainland. Its diet consists primarily of small fis ...

Birds of Antarctica Birds of New Zealand Birds of islands of the Atlantic Ocean Birds of subantarctic islands Birds of the Southern Ocean Birds of the Indian Ocean Birds of the Campbell Islands Fauna of the Prince Edward Islands Fauna of Heard Island and McDonald Islands