The snowy-crowned tern (''Sterna trudeaui''), also known as Trudeau's tern, 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 native to Argentina, Brazil, Chile, Uruguay, and possibly Paraguay, and also

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 Peru and the Falkland Islands.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

Taxonomy and systematics

Some genetic data indicate that the snowy-crowned tern and several other closely related terns belong in a genus separate from ''Sterna''. At the least, the snowy-crowned and

Forster's tern Forster's tern (''Sterna forsteri'') is a tern in the family Laridae. The genus name ''Sterna'' is derived from Old English "stearn", "tern", and ''forsteri'' commemorates the naturalist Johann Reinhold Forster. It breeds inland in North America ...

(''S. forsteri'') are

sister species In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

. The snowy-crowned tern 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 "unisp ...

. The snowy-crowned tern was first described by the American ornithologist

John James Audubon John James Audubon (born Jean-Jacques Rabin, April 26, 1785 – January 27, 1851) was a French-American Autodidacticism, self-trained artist, natural history, naturalist, and ornithology, ornithologist. His combined interests in art and ornitho ...

in 1838. He had been sent a specimen by his friend Dr. James de Berty Trudeau (1817–1887) of Louisiana, who had reportedly found several of the terns at

Great Egg Harbor Bay Great Egg Harbor Bay (or Great Egg Harbor) is a bay between Atlantic and Cape May counties along the southern New Jersey coast. The name derives from Dutch explorer Cornelius Jacobsen May's description of the plentiful birds laying eggs, naming th ...

, New Jersey. Audubon named the bird in his honor.

Description

The snowy-crowned tern is long with a wingspan of and weighs . It has a rather blocky head, a thick neck, long wings, and a forked tail. The sexes have the same plumage. Adults in breeding plumage have a white head and neck with a black band through the eye. Their upperparts are pale gray with a whitish rump and uppertail

coverts A covert feather or tectrix on a bird is one of a set of feathers, called coverts (or ''tectrices''), which cover other feathers. The coverts help to smooth airflow over the wings and tail. Ear coverts The ear coverts are small feathers behind t ...

. Their underparts are grayish white. Their upperwing is pale gray with silvery

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 ...

and the underwing is white. Their iris is brown and their bill orange with a yellow tip and a black band separating the colors. Their legs and feet are reddish orange. Non-breeding adults are similar to breeding ones, but with a grayer stripe on the face, more intense silvery on the primaries, and a black bill with a yellowish tip. Juveniles have a black and white pattern on their back, a black band near the end of the tail, a black bill, and dark legs.Gochfeld, M., J. Burger, and E. F. J. Garcia (2020). Snowy-crowned Tern (''Sterna trudeaui''), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.truter.01 retrieved February 17, 2023

Distribution and habitat

The snowy-crowned tern breeds from southeastern Brazil south through Uruguay to Argentina's

Buenos Aires Province Buenos Aires, officially the Buenos Aires Province, is the largest and most populous Provinces of Argentina, Argentine province. It takes its name from the city of Buenos Aires, the capital of the country, which used to be part of the province an ...

and also in Chile between the provinces of

Aconcagua Aconcagua () is a mountain in the Principal Cordillera of the Andes mountain range, in Mendoza Province, Argentina. It is the highest mountain in the Americas, the highest outside Asia, and the highest in both the Western Hemisphere and the ...

and Llanquihue. Outside the breeding season it ranges along the Atlantic coast as far north as the

Rio de Janeiro Rio de Janeiro, or simply Rio, is the capital of the Rio de Janeiro (state), state of Rio de Janeiro. It is the List of cities in Brazil by population, second-most-populous city in Brazil (after São Paulo) and the Largest cities in the America ...

area and on the Pacific coast as far north as the

Department of Ica Ica (; ) is a Subdivisions of Peru, department and region of Peru. It borders the Pacific Ocean on the west; the Lima Region on the north; the Huancavelica Region, Huancavelica and Ayacucho Region, Ayacucho regions on the east; and the Arequipa ...

in Peru. It has appeared as a vagrant as far south as the

Straits of Magellan The Strait of Magellan (), also called the Straits of Magellan, is a navigable sea route in southern Chile separating mainland South America to the north and the Tierra del Fuego archipelago to the south. Considered the most important natural ...

and on the

Falkland Islands The Falkland Islands (; ), commonly referred to as The Falklands, is an archipelago in the South Atlantic Ocean on the Patagonian Shelf. The principal islands are about east of South America's southern Patagonian coast and from Cape Dub ...

. Undocumented sight records in Paraguay lead the South American Classification Committee of 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 ...

to treat it as hypothetical in that country. The purported type locality of New Jersey is not supported by any documented North American records. The snowy-crowned tern inhabits coastal and inland wetlands both fresh and saline, though it favors freshwater landscapes. It mostly breeds on lagoons in the

Pampas The Pampas (; from Quechua 'plain'), also known as the Pampas Plain, are fertile South American low grasslands that cover more than and include the Argentine provinces of Buenos Aires, La Pampa, Santa Fe, Entre Ríos, and Córdoba; all o ...

and

Patagonia Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...

but also on islands in coastal lagoons.

Behavior

Feeding

The snowy-crowned tern feeds mostly on fish but also on insects. It forages over shallow water along the edges of wetlands, rivers, and lagoons and over plowed fields. It takes fish by plunge-diving.

Breeding

The snowy-crowned tern's breeding biology is not fully understood. Its breeding season appears to include October to December. It nests in colonies, often sharing areas with

brown-hooded gull The brown-hooded gull (''Chroicocephalus maculipennis'') is a species of gull, found in South America in Argentina, southeastern Brazil, Chile, Uruguay, and in the South Atlantic Ocean on the Falkland Islands. Its specific epithet, '' maculipenni ...

s (''Larus maculipennis''). It builds a floating platform nest in shallow water, either free-floating or anchored to emergent vegetation. Both sexes vigorously defend the nest. The clutch size is two to four eggs, but usually three. The incubation period, time to fledging, and details of parental care are not known.

Vocalization

The snowy-crowned tern's call is "a series of rapid notes "je-je-je-je", or a short, grating "jeeer"."

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 ...

has assessed the snowy-crowned tern as being of Least Concern. It has a fairly large range. Its population is estimated at below 6700 mature individuals and is believed to be stable. "The species only nests in large wetlands, suggesting habitat loss, especially through abstraction of surface water for agricultural use, may be a potentially serious problem."

References

{{Taxonbar, from=Q997524 Sterna Birds of Argentina Birds of Chile Birds of Uruguay Birds of the South Region

Snowy-crowned tern The snowy-crowned tern (''Sterna trudeaui''), also known as Trudeau's tern, is a species of bird in subfamily Sterninae of the family Laridae, the gulls, terns, and skimmers. It is native to Argentina, Brazil, Chile, Uruguay, and possibly Parag ...

Taxonomy articles created by Polbot