The Caspian tern (''Hydroprogne caspia'') is a species of

tern Terns are seabirds in the family Laridae that have a worldwide distribution and are normally found near the sea, rivers, or wetlands. Terns are treated as a subgroup of the family Laridae which includes gulls and skimmers and consists of ...

, with a subcosmopolitan but scattered distribution. Despite its extensive range, it is

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

of its genus, and has no accepted

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

. The genus name is from Ancient Greek ''hudros'', "water", and

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''progne'', "

swallow The swallows, martins, and saw-wings, or Hirundinidae, are a family of passerine songbirds found around the world on all continents, including occasionally in Antarctica. Highly adapted to aerial feeding, they have a distinctive appearance. The ...

". The specific ''caspia'' is from Latin and, like the English name, refers to the

Caspian Sea The Caspian Sea is the world's largest inland body of water, often described as the world's largest lake or a full-fledged sea. An endorheic basin, it lies between Europe and Asia; east of the Caucasus, west of the broad steppe of Central Asi ...

Description

It is the world's largest tern with a length of , a wingspan of and a weight of . Adult birds have black legs, and a long thick red-orange bill with a small black tip. They have a white head with a black cap and white neck, belly, and tail. The upper wings and back are pale grey; the underwings are pale with dark primary feathers. In-flight, the tail is less forked than other terns, and wingtips are black on the underside. In winter, the black cap is still present (unlike many other terns), but with some white streaking on the forehead. The call is a loud heron-like croak.

Distribution and habitat

Their breeding habitat is large lakes and ocean coasts in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the C ...

(including the

Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes in the mid-east region of North America that connect to the Atlantic Ocean via the Saint Lawrence River. There are five lakes ...

), and locally in Europe (mainly around the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and from ...

and Black Sea),

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an area ...

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

, and

Australasia Australasia is a region that comprises Australia, New Zealand and some neighbouring islands in the Pacific Ocean. The term is used in a number of different contexts, including geopolitically, physiogeographically, philologically, and ecologi ...

( Australia and

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island country ...

). North American birds migrate to southern coasts, the

West Indies The West Indies is a subregion of North America, surrounded by the North Atlantic Ocean and the Caribbean Sea that includes 13 independent island countries and 18 dependencies and other territories in three major archipelagos: the Greater ...

and northernmost South America. European and Asian birds spend the non-breeding season in the

Old World The "Old World" is a term for Afro-Eurasia that originated in Europe , after Europeans became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia, which were previously thought of by th ...

tropics. African and Australasian birds are resident or disperse over short distances. In 2016, a nest of the Caspian tern was found in the

Cape Krusenstern National Monument Cape Krusenstern National Monument and the colocated Cape Krusenstern Archeological District is a U.S. National Monument and a National Historic Landmark centered on Cape Krusenstern in northwestern Alaska. The national monument was one of fif ...

in northwestern

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

, 1,000 miles further north than any previous sighting. This development was part of a general trend in Alaska of species moving to the north, a tendency ascribed to

global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

. The global population is about 50,000 pairs; numbers in most regions are stable, but the Baltic Sea population (1400–1475 pairs in the early 1990s) is declining and of conservation concern. The Caspian tern is one of the species to which the ''Agreement on the Conservation of African-Eurasian Migratory Waterbirds'' (

AEWA The Agreement on the Conservation of African-Eurasian Migratory Waterbirds, or African-Eurasian Waterbird Agreement (AEWA) is an independent international treaty developed under the auspices of the United Nations Environment Programme's Conventio ...

) applies.

Behaviour

Feeding

They feed mainly on

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

, which they dive for, hovering high over the water and then plunging. They also occasionally eat large

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of ...

s, the young and eggs of other birds and rodents. They may fly up to from the breeding colony to catch fish; they often fish on freshwater lakes as well as at sea.

Breeding

Breeding is in spring and summer, with one to three pale blue-green eggs, with heavy brown spotting, being laid. They nest either together in colonies, or singly in mixed colonies of other tern and

gull Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns and skimmers and only distantly related to auks, and even more distantly to waders. Until the 21st century, ...

species. The nest is on the ground among gravel and sand, or sometimes on vegetation; incubation lasts for 26–28 days. The chicks are variable in plumage pattern, from pale creamy to darker grey-brown; this variation assists adults in recognizing their own chicks when returning to the colony from feeding trips. Fledging occurs after 35–45 days.

Gallery

File: Caspian Tern takeoff RWD.jpg, Preparing for takeoff File: Caspian tern in flight at DeKorte Park (42079).jpg, Caspian tern in flight File:Two caspian terns.png, Two Caspian terns in flight

References

External links

Caspian Tern species text in The Atlas of Southern African Birds
* * * * * * * * {{Taxonbar, from=Q27129

Caspian tern The Caspian tern (''Hydroprogne caspia'') is a species of tern, with a subcosmopolitan but scattered distribution. Despite its extensive range, it is monotypic of its genus, and has no accepted subspecies. The genus name is from Ancient Greek ...

Birds of Central Asia Birds of Eurasia Birds of Madagascar Birds of North America Birds of the Dominican Republic Birds of Oceania Birds of West Africa Birds of Africa

Cosmopolitan birds Holarctic birds