The black-necked swan (''Cygnus melancoryphus'') is a species of

waterfowl Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which i ...

in the tribe

Cygnini Swans are birds of the genus ''Cygnus'' within the family Anatidae. The swans' closest relatives include the geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometim ...

of the subfamily

Anserinae The Anserinae are a subfamily in the waterfowl family Anatidae. It includes the swans and the true Goose, geese. Under alternative systematics, systematical concepts (see e.g., Terres & NAS, 1991), it is split into two subfamilies, the Anserina ...

.HBW and BirdLife International (2021) Handbook of the Birds of the World and BirdLife International digital checklist of the birds of the world. Version 6. Available at: http://datazone.birdlife.org/userfiles/file/Species/Taxonomy/HBW-BirdLife_Checklist_v6_Dec21.zip retrieved August 7, 2022 It is found in

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

Uruguay Uruguay, officially the Oriental Republic of Uruguay, is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast, while bordering the Río de la Plata to the south and the A ...

, and 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 ...

.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 24 July 2022. Species Lists of Birds for South American Countries and Territories. https://www.museum.lsu.edu/~Remsen/SACCCountryLists.htm retrieved July 24, 2022

Taxonomy and systematics

The black-necked swan has occasionally been placed by itself in the genus ''Sthenelides''. Its closest relatives are the

black swan The black swan (''Cygnus atratus'') is a large Anatidae, waterbird, a species of swan which breeds mainly in the southeast and southwest regions of Australia. Within Australia, the black swan is nomadic, with erratic migration patterns dependent ...

(''C. atratus'') and

mute swan The mute swan (''Cygnus olor'') is a species of swan and a member of the waterfowl family Anatidae. It is native to much of Eurasia, and (as a rare winter visitor) the far north of Africa. It is an introduced species in North America, home to ...

(''C. olor''). 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 "unisp ...

Description

The black-necked swan is the only member of its genus that breeds in the

neotropic The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In biogeogra ...

s and is the largest waterfowl native to South America. Adults are long with a wingspan of . Males weigh and females . The sexes are alike. Adults' body plumage is white and the neck and head black; the latter usually has a white stripe behind the eye. They have a prominent red knob at the base of their bill. Juveniles are grayish rather than white and lack the knob until their third or fourth year.

Distribution and habitat

The black-necked swan is found in the southern tier of South America. It nests from

Tierra del Fuego Tierra del Fuego (, ; Spanish for "Land of Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South America, South American mainland, across the Strait of Magellan. The archipelago consists of the main is ...

north to central Chile, Uruguay, and

Rio Grande do Sul Rio Grande do Sul (, ; ; "Great River of the South") is a Federative units of Brazil, state in the South Region, Brazil, southern region of Brazil. It is the Federative units of Brazil#List, fifth-most populous state and the List of Brazilian s ...

in extreme southern Brazil. It withdraws from the southern half of Argentina in winter and is then found as far north as Brazil's

São Paulo São Paulo (; ; Portuguese for 'Paul the Apostle, Saint Paul') is the capital of the São Paulo (state), state of São Paulo, as well as the List of cities in Brazil by population, most populous city in Brazil, the List of largest cities in the ...

state. It is a year-round resident of the Falkland Islands.

Vagrants 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, ...

have been found on

Juan Fernández Island ''Juan'' is a given name, the Spanish and Manx versions of ''John''. The name is of Hebrew origin and has the meaning "God has been gracious." It is very common in Spain and in other Spanish-speaking countries around the world and in the Philippi ...

, the

South Orkney Islands The South Orkney Islands are a group of List of Antarctic and sub-Antarctic islands, islands in the Southern Ocean, about north-east of the tip of the Antarctic Peninsula South Shetland Islands The South Shetland Islands are a group of List of Antarctic and subantarctic islands, Antarctic islands located in the Drake Passage with a total area of . They lie about north of the Antarctic Peninsula, and between southwest of the n ...

, and the

Antarctic Peninsula The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martin 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 Antarctica. ...

. The black-necked swan inhabits freshwater

marshes In ecology, a marsh is a wetland that is dominated by herbaceous plants rather than by woody plants.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p More in general ...

and swamps, shallow lakes, brackish

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ...

s, and sheltered coastal sites. On the mainland of South America, it is often found near human habitation but shuns built-up areas in the Falklands. It is generally found at low elevations but non-breeding flocks can be found as high as in the Andes of southern Argentina. The wetlands created in Chile by the

1960 Valdivia earthquake The 1960 Valdivia earthquake and tsunami () or the Great Chilean earthquake (''Gran terremoto de Chile'') occurred on 22 May 1960. Most studies have placed it at 9.5–9.6 on the moment magnitude scale, while some studies have placed the magnitu ...

, such as

Carlos Anwandter Nature Sanctuary Carlos Anwandter Nature Sanctuary () is protected wetland in Cruces River about north of Valdivia, Chile. The sanctuary is named after the German politician Carlos Anwandter who settled in Valdivia in 1850. This sanctuary provides a home for man ...

on the

Cruces River The Cruces River () is a river in south-central Chile. Río Cruces originates from hills near the Villarica volcano and flows then in south-west direction. The southern and final part of the river flows in a south-south-west direction followin ...

, have become important population centers for the black-necked swan.Ramirez, C., E. Carrasco, S. Mariani & N. Palacios. 2006. La desaparición del luchecillo (''Egeria densa'') del Santuario del Rio Cruces (Valdivia, Chile): una hipótesis plausible. Ciencia & Trabajo, 20: 79-86 The population in this sanctuary has fluctuated widely over the years, reaching a low of 214 in January 2008 and a peak of 22,419 in May 2020 before plumbing to 2,782 in May 2022.

Behavior

Feeding

The black-necked swan's diet is almost entirely vegetarian. It feeds on aquatic plants like '' Chara'', ''

Potamogeton ''Potamogeton'' is a genus of aquatic, mostly freshwater, plants of the family Potamogetonaceae. Most are known by the common name pondweed, although many unrelated plants may be called pondweed, such as Canadian pondweed (''Elodea canadensis' ...

'', ''

Typha ''Typha'' is a genus of about 30 species of monocotyledonous flowering plants in the family Typhaceae. These plants have a variety of common names, in British English as bulrushStreeter D, Hart-Davies C, Hardcastle A, Cole F, Harper L. 2009. ' ...

''; algae such as ''Aphantotece'' and ''Rhyzoclonium''; and presumably small numbers of aquatic invertebrates. In parts of Chile its principal food is ''

Egeria densa ''Elodea densa'', the large-flowered waterweed or Brazilian waterweed, is a species of '' Elodea'' native to warm temperate South America in southeastern Brazil, Argentina, Chile and Uruguay. It is considered a problematic invasive species due t ...

''. It forages mostly by immersing its head and neck and by surface feeding, but also upends to reach deeper. In times of drought it has been observed grazing in meadows and pastures.

Breeding

The black-necked swan's breeding season varies geographically. In the far south of its range, it breeds from July to November but ends as early as September in the northern parts. In the Falklands, it breeds between August and November. The exact timing of breeding appears dependent on rainfall. The species is believed to form long-term pair bonds. Its nest is a mound of vegetation constructed by both members of a pair on a small islet or partially floating in a reedbed. The clutch size is four to eight eggs. Males guard females during the 34- to 36-day incubation period. Captive nestlings fledged about 100 days after hatch.

Vocalization

The black-necked swan is mostly silent outside the breeding season. During that time, both sexes give a "soft, musical 'Whee-whee-whee' with the accent on the initial syllable", repeating it to challenge intruders. The call is also used to maintain contact between members of a pair. Males also give "a musical 'hooee-hoo-hoo'."

Diseases

Black-necked swans can contract

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 ...

. In March 2023

influenza A virus subtype H5N1 Influenza A virus subtype H5N1 (A/H5N1) is a subtype of the influenza A virus, which causes the disease avian influenza (often referred to as "bird flu"). It is enzootic (maintained in the population) in many bird populations, and also panzoo ...

was detected in black-necked swan populations in

, Chile and Estación Tapia, Uruguay. As on May 30, 2023, three more black-necked swans were found dead due to influenza H5N1 in Lagoa da Mangueira,

Taim Ecological Station The Taim Ecological Station () is a federally-administered ecological station in the state of Rio Grande do Sul, Brazil. Location The coastal marine ecological station, which has an area of , was established on 21 July 1986. It is administered b ...

, Brasil. This raises the total at that station to 63.

Status and conservation

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 black-necked swan as being of Least Concern. It has a very large range, and though its population size is not known, it is believed to be stable. No immediate threats have been identified. It is widespread and generally common. Large-scale hunting in the 18th and 19th centuries extirpated it from much of Chile but it has recolonized those areas. Some egg collecting and hunting still occur, however. The species occurs in several protected areas in mainland Argentina, in which country the population is estimated at 50,000.

Gallery

File:Blackneck swan pair hornopiren chile feb 2010.jpg File:Cygnus melanocoryphus at the Denver Zoo-2012 03 12 1029.jpg File:Cygnus melanocoryphus at the Denver Zoo-2012 03 12 1033.jpg File:Black Necked Swans at the Philadelphia Zoo (cropped).jpg File:Black-necked Swan SMTC.jpg File:Cygnus melancoryphus MHNT.ZOO.2010.11.11.1.jpg

References

External links

* (for Argentina, Brazil, Chile, Falkland Islands, Uruguay) with RangeMap
Black-necked Swan photo gallery
VIREO

black-necked swan The black-necked swan (''Cygnus melancoryphus'') is a species of waterfowl in the tribe Cygnini of the subfamily Anserinae.HBW and BirdLife International (2021) Handbook of the Birds of the World and BirdLife International digital checklist of ...

Birds of Chile Birds of the Falkland Islands Birds of the Pampas Birds of Patagonia

Swans