Thalasseus
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''Thalasseus'', the crested terns, is a genus of eight species of medium-large to large
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 Laridae is a family of seabirds in the order Charadriiformes that includes the gulls, terns (including white terns), noddies, and skimmers. It includes around 100 species arranged into 22 genera. They are an adaptable group of mostly aerial bird ...
. The species have a worldwide distribution in temperate and tropical seas, mostly between about 43° N and S latitude, but to 60° N in the warm waters of the
North Atlantic Current The North Atlantic Current (NAC), also known as North Atlantic Drift and North Atlantic Sea Movement, is a powerful warm western boundary current within the Atlantic Ocean that extends the Gulf Stream northeastward. Characteristics The NAC ...
in the eastern North Atlantic Ocean; they do not occur in colder arctic or antarctic waters. Several of the species are abundant and well-known birds in their ranges; one is however extremely rare and critically endangered. This genus had originally been distinguished by
Friedrich Boie Friedrich Boie (4 June 1789 – 3 March 1870) was a German entomologist, herpetologist, ornithologist, and lawyer.Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). ''The Eponym Dictionary of Reptiles''. Baltimore: Johns Hopkins Universi ...
in 1822, but had been little used (with one exception in 1978) until a 2005 study confirmed the need for a separate genus for the crested terns. ''Thalasseus'' terns are large for terns, from 35–53 cm long, with lesser crested tern marginally the smallest, and greater crested tern marginally the largest. The underside plumage is white in all species, while the wings and back vary from pale silvery grey to dark grey. They have long thin sharp bills, a shade of yellow or orange except in the
Sandwich tern The Sandwich tern (''Thalasseus sandvicensis'') is a tern in the family Laridae. It is very closely related to the lesser crested tern (''T. bengalensis''), Chinese crested tern (''T. bernsteini''), Cabot's tern (''T. acuflavidus''), and el ...
and
Cabot's tern Cabot's tern (''Thalasseus acuflavidus'') is a species of bird in subfamily Sterninae of the family Laridae, the gulls, terns, and skimmers. It is found in the eastern United States and Middle America, the Caribbean, Trinidad and Tobago, and i ...
where the bills are black with yellow tips (variably more extensively yellow in one subspecies of Cabot's tern). All species have a shaggy black crest, which is erectile and used in the courtship display. In winter, the foreheads become white to a variable extent. They breed in very dense colonies on coasts and islands, and exceptionally inland on suitable large freshwater lakes close to the coast. They nest in a ground scrape. ''Thalasseus'' terns feed by plunge-diving for fish, almost invariably from the sea. They usually dive directly, and not from the "stepped-hover" favoured by, for example, the
Arctic tern The Arctic tern (''Sterna paradisaea'') is a tern in the family Laridae. This bird has a circumpolar breeding distribution covering the Arctic and sub-Arctic regions of Europe (as far south as Brittany), Asia, and North America (as far south ...
. The offering of fish by the male to the female is part of the courtship display. Their habit of breeding in very dense colonies made them highly vulnerable to the 2021–2023
highly pathogenic avian influenza Avian influenza, also known as avian flu or bird flu, is a disease caused by the influenza A virus, which primarily affects birds but can sometimes affect mammals including humans. Wild aquatic birds are the primary host of the influenza A viru ...
(HPAI) outbreaks, with mass mortality in numerous colonies of Sandwich tern in particular, and also West African crested tern.


Taxonomy

The genus ''Thalasseus'' was described by the German zoologist
Friedrich Boie Friedrich Boie (4 June 1789 – 3 March 1870) was a German entomologist, herpetologist, ornithologist, and lawyer.Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). ''The Eponym Dictionary of Reptiles''. Baltimore: Johns Hopkins Universi ...
in 1822. The
type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...
was subsequently designated as the
sandwich tern The Sandwich tern (''Thalasseus sandvicensis'') is a tern in the family Laridae. It is very closely related to the lesser crested tern (''T. bengalensis''), Chinese crested tern (''T. bernsteini''), Cabot's tern (''T. acuflavidus''), and el ...
(''Thalasseus sandvicensis''). The generic name is derived from the
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 ...
''Thalassa'' meaning "sea".


List of species

The genus contains eight species: An early
Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
closely resembles a modern royal tern. It may be an unexpectedly early (3.7–4.8 million years before present) specimen of that species, or an ancestral member of the crested tern group.Olson, S., Rasmussen, P.C. Miocene and Pliocene birds from the Lee Creek Mine, North Carolina, in Ray, C. E. & Bohaska, D.J. (2001). Geology and Paleontology of the Lee Creek Mine, North Carolina, III. ''Smithsonian Contributions to Paleobiology'' 90: 233-365.


References

{{Taxonbar, from=Q133577 Bird genera Taxa named by Friedrich Boie