Cabot's Tern
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Cabot's tern (''Thalasseus acuflavidus'') is a species of bird in subfamily Sterninae of 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 gulls, terns, and skimmers. It is found in the eastern
United 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 ...
and Middle America, the Caribbean, Trinidad and Tobago, and in every mainland South American country except Bolivia and Paraguay, though rare in Chile.Remsen, J. V., Jr., J. I. Areta, E. Bonaccorso, S. Claramunt, A. Jaramillo, D. F. Lane, J. F. Pacheco, M. B. Robbins, F. G. Stiles, and K. J. Zimmer. 30 January 2023. Species Lists of Birds for South American Countries and Territories. https://www.museum.lsu.edu/~Remsen/SACCCountryLists.htm retrieved January 30, 2023 It is also a
vagrant Vagrancy is the condition of wandering homelessness without regular employment or income. Vagrants usually live in poverty and support themselves by travelling while engaging in begging, scavenging, or petty theft. In Western countries, ...
in eastern Canada and western Europe.


Taxonomy and systematics

Cabot's tern was long placed in 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 determined that this arrangement was paraphyletic. It is now restricted to the typi ...
'' but since the early 2000s has been in its present genus ''Thalasseus''. Its further taxonomy is not settled. The
International Ornithological Committee The International Ornithologists' Union (IOU) is an international organization for the promotion of ornithology. It links basic and applied research and nurtures education and outreach activities. Specifically, the IOU organizes and funds global co ...
(IOC) follows Efe et al. in part and treats it as a species with two subspecies, the
nominate Nomination is part of the process of selecting a candidate for either election to a public office, or the bestowing of an honor or award. A collection of nominees narrowed from the full list of candidates is a short list. Political office In th ...
''T. a. acuflavidus'' ( Cabot, S, 1847) and ''T. a. eurygnathus'' (
Saunders Saunders is a surname of English and Scottish origin, derived from ''Sander'', a mediaeval form of Alexander.See also: Sander (name) People * Ab Saunders (1851–1883), American cowboy and gunman * Al Saunders (born 1947), American football c ...
, 1876). The
American Ornithological Society The American Ornithological Society (AOS) is an ornithological organization based in the United States. The society was formed in October 2016 by the merger of the American Ornithologists' Union (AOU) and the Cooper Ornithological Society. Its ...
and the
Clements taxonomy ''The Clements Checklist of Birds of the World'' is a book by Jim Clements which presents a list of the bird species of the world. The most recent printed version is the sixth edition (2007), but has been updated yearly, the last version in 202 ...
have not yet accepted Efe et al. and treat those two taxa as subspecies of 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 ...
(''T. sandvicensis'').Chesser, R. T., S. M. Billerman, K. J. Burns, C. Cicero, J. L. Dunn, B. E. Hernández-Baños, R. A. Jiménez, A. W. Kratter, N. A. Mason, P. C. Rasmussen, J. V. Remsen, Jr., D. F. Stotz, and K. Winker. 2022. Check-list of North American Birds (online). American Ornithological Society. https://checklist.aou.org/taxa Remsen, J. V., Jr., J. I. Areta, E. Bonaccorso, S. Claramunt, A. Jaramillo, D. F. Lane, J. F. Pacheco, M. B. Robbins, F. G. Stiles, and K. J. Zimmer. Version 30 January 2023. A classification of the bird species of South America. American Ornithological Society. https://www.museum.lsu.edu/~Remsen/SACCBaseline.htm retrieved January 30, 2023Clements, J. F., T. S. Schulenberg, M. J. Iliff, T. A. Fredericks, J. A. Gerbracht, D. Lepage, S. M. Billerman, B. L. Sullivan, and C. L. Wood. 2022. The eBird/Clements checklist of birds of the world: v2022. Downloaded from https://www.birds.cornell.edu/clementschecklist/download/ retrieved November 10, 2022
BirdLife International BirdLife International is a global partnership of non-governmental organizations that strives to conserve birds and their habitats. BirdLife International's priorities include preventing extinction of bird species, identifying and safeguarding i ...
's ''
Handbook of the Birds of the World The ''Handbook of the Birds of the World'' (HBW) is a multi-volume series produced by the Spanish publishing house Lynx Edicions in partnership with BirdLife International. It is the first handbook to cover every known living species of bird. ...
'' (HBW) follows a different conclusion to Efe et al. than the IOC by merging ''eurygnathus'' into ''acuflavidus'' but treats the merged taxon as one of two subspecies of the Sandwich tern.HBW and BirdLife International (2022) Handbook of the Birds of the World and BirdLife International digital checklist of the birds of the world. Version 7. Available at: http://datazone.birdlife.org/userfiles/file/Species/Taxonomy/HBW-BirdLife_Checklist_v7_Dec22.zip retrieved December 13, 2022 However, another study in 2017 confirmed Efe et al's results (as well as additionally proposing the splitting of West African crested tern from
royal tern The royal tern (''Thalasseus maximus'') is a tern in the family Laridae. The species is endemic to the Americas, though vagrants have been identified in Europe.Buckley, P. A. and F. G. Buckley (2020). Royal Tern (Thalasseus maximus), version 1. ...
), as did a further 2022 study which confirmed both the above ''Thalasseus'' splits. Some authors treat subspecies ''T. a. eurygnathus'' as a separate species, the "Cayenne tern" but this has not been widely accepted. The genus ''Thalasseus'' is
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 ...
for "fisherman", derived from ''thalassa'', "sea". The
specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...
''acuflavidus'' is from
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
''acus'', "needle", and ''flavidus'', "yellowish".


Description

Cabot's tern is a member of the "crested tern" group. It is long with a wingspan of about . The nominate subspecies ''T. a. acuflavidus'' weighs . The Caribbean population of ''T. a. eurygnathus'' weighs and the far southern population . The sexes have the same plumage and there is little difference in plumage between the subspecies. Adults in breeding plumage have a black cap and a mostly white body with a pale gray back and sometimes a rosy flush on the underparts. Their tail is forked and white. The upper side of their wing is mostly pale gray with darker
primaries Primary elections or primaries are elections held to determine which candidates will run in an upcoming general election. In a partisan primary, a political party selects a candidate. Depending on the state and/or party, there may be an "open pri ...
. Their legs and feet are all black or black with yellow soles and their iris is dark brown to black. Non-breeding adults have a white forehead and mid-crown; their crest is black. The subspecies differ mainly in bill color: The nominate's is black with a yellow tip of somewhat variable extent; that of ''T. a. eurygnathus'' is mostly to completely yellow.Shealer, D., J. S. Liechty, A. R. Pierce, P. Pyle, and M. A. Patten (2020). Sandwich Tern (''Thalasseus sandvicensis''), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.santer1.01 retrieved February 16, 2023 Cabot's tern is very similar to Sandwich tern, sharing the black bill with a yellow tip, but differs in the bill being obviously stouter, and also differs in molt timing, losing its black forehead earlier in the summer. Its juveniles also lack the scaly pattern of juvenile Sandwich terns, being a plainer grey (though they can be confused with first-winter plumage of Sandwich tern).


Distribution and habitat

The nominate subspecies of Cabot's tern breeds on the U.S. coast from
Chesapeake Bay The Chesapeake Bay ( ) is the largest estuary in the United States. The bay is located in the Mid-Atlantic (United States), Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula, including parts of the Ea ...
south and around the Gulf of Mexico to Belize, and on the Bahamas, the
Greater Antilles The Greater Antilles is a grouping of the larger islands in the Caribbean Sea, including Cuba, Hispaniola, Puerto Rico, and Jamaica, together with Navassa Island and the Cayman Islands. Seven island states share the region of the Greater Antille ...
, and other Caribbean islands. It winters in southern Florida and the entire Gulf and Caribbean coasts, the Antilles, and in South America commonly in Colombia, Ecuador, and Peru though a few go as far south as Chile or east in northern Brazil. Subspecies ''T. a. eurygnathus'' is mostly a year-round resident from the north and east coasts of South America and the islands near it, south along the coast of Brazil to southern Argentina; a few breed as far north as Puerto Rico. Cabot's tern is wholly a coastal species, and favors warm water. During the breeding season it inhabits barrier islands, dredge spoil islands, and in the Caribbean low-lying sand or coral cays. It generally uses bare ground but will nest on prostrate vegetation or mats of purslane (''Sporobolus virginianus''). It overwinters on sand beaches and sandbars, barrier islands, and reefs along coasts and also along the Panama Canal and short distances up rivers that empty into salt water.


Behavior


Migration

Cabot's tern is partially migratory, withdrawing from the northernmost part of its breeding range for winter. Its migratory routes are not known in detail but are believed to follow coasts. Fall migration is protracted and spring's is more rapid. Birds that overwinter on the Pacific coast of South America apparently cross from the Caribbean at the Isthmus of Panama. A few banded individuals of subspecies ''T. a. acuflavidus'' have wandered to the Netherlands and the United Kingdom.


Feeding

Cabot's tern is a powerful flyer, and feeds almost exclusively by plunge-diving from up to high. It sometimes goes completely under water in its dive. It often forages in small flocks and usually within of shore, though it apparently goes further out from the Texas shore. Its diet is mostly fish, with members of families Ammodytidae, Atherinopsidae,
Clupeidae Clupeidae is a family of clupeiform ray-finned fishes, comprising, for instance, the herrings and sprats. Many members of the family have a body protected with shiny cycloid (very smooth and uniform) scales, a single dorsal fin, and a fusiform ...
,
Engraulidae An anchovy is a small, common forage fish of the family Engraulidae. Most species are found in marine waters, but several will enter brackish water, and some in South America are restricted to fresh water. More than 140 species are placed in 1 ...
, and
Sciaenidae Sciaenidae is a family (biology), family of ray-finned fishes belonging to the Order (biology), order Acanthuriformes. They are commonly called drums or croakers in reference to the repetitive throbbing or drumming sounds they make. The family co ...
identified as prey. It eats smaller amounts of squid, shrimp, and insects.


Breeding

Cabot's terns apparently court and form pairs during spring migration before reaching the nesting grounds. Males make display flights or posture on the ground. The species nests in areas with sparse or no vegetation. The nest is a simple scrape made by both sexes; they may add a few pieces of shell or seaweed. The typical clutch size is one egg though two are not uncommon. The incubation period is about 24 days in the north and averages about 29 days in the far south. Both sexes incubate, and apparently share the duty equally after the first few days. Chicks are semi-precocial and can thermoregulate about five days after hatch. They depend on the parents for food; both parents provide it until fledging and usually the female alone after that. Nest defense is shared equally. Fledging occurs about 27 to 29 days after hatch.


Vocalization

As of early 2024
xeno-canto xeno-canto is a citizen science project and repository in which volunteers record, upload and annotate recordings of bird calls and sounds of orthoptera and bats. Since it began in 2005, it has collected over 575,000 sound recordings from more th ...
had 53 recordings of Cabot's tern from the Americas, and a further three of presumed Cabot's terns misclassified among the very many of Sandwich tern. The
Cornell Lab of Ornithology The Cornell Lab of Ornithology is a member-supported unit of Cornell University in Ithaca, New York, which studies birds and other wildlife. It is housed in the Imogene Powers Johnson Center for Birds and Biodiversity in Sapsucker Woods Sanctuar ...
's
Macaulay Library The Macaulay Library is the world's largest archive of animal media. It includes more than 71 million photographs, 2.6 million audio recordings, and over three hundred thousand videos covering 96 percent of the world's bird species. There are an ev ...
has additional recordings. The species' main call has been described as ''kerr-ick'', ''kjerr-it'', ''keerik'', and ''kreejik''. It has a variety of other calls as well.


Status

The
IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...
follows HBW taxonomy so has not assessed Cabot's tern separately from Sandwich tern ''
sensu lato ''Sensu'' is a Latin word meaning "in the sense of". It is used in a number of fields including biology, geology, linguistics, semiotics, and law. Commonly it refers to how strictly or loosely an expression is used in describing any particular co ...
''. Disturbance of nesting colonies by humans appears to be the major threat to the species as a whole.


Gallery

File:Cabot's Terns, Fort de Soto, Florida (49154902928).jpg, ''T. a. acuflavidus'' at Fort de Soto,
Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
File:Cabot's Tern fishing.jpg, Fishing near
Tampa Bay Tampa Bay is a large natural harbor and shallow estuary connected to the Gulf of Mexico on the west-central coast of Florida, comprising Hillsborough Bay, McKay Bay, Old Tampa Bay, Middle Tampa Bay, and Lower Tampa Bay. The largest freshwater i ...
, Florida File:Cabot's Tern in Flight.jpg, In flight, Sanibel, Florida File:Thalasseus acuflavidus eurygnathus, Florianopolis, Santa Catarina, Brazil 1.jpg, ''T. a. eurygnathus'' or intergrade with ''T. a. acuflavidus'', with partially yellow bill. Santa Catarina, Brazil. File:Thalasseus acuflavidus eurygnathus, Santa Vitória do Palmar, Rio Grande do Sul, Brazil 1.jpg, ''T. a. eurygnathus'' with fully yellow bills. Rio Grande do Sul, Brazil.


References

{{Taxonbar, from=Q3498794 Cabot's tern Native birds of the Southeastern United States Birds of the Americas Cabot's tern