The cocoi heron (''Ardea cocoi'') is a species of long-legged wading bird in the

heron Herons are long-legged, long-necked, freshwater and coastal birds in the family Ardeidae, with 75 recognised species, some of which are referred to as egrets or bitterns rather than herons. Members of the genus ''Botaurus'' are referred to as bi ...

family

Ardeidae Herons are long-legged, long-necked, freshwater and coastal birds in the family Ardeidae, with 75 recognised species, some of which are referred to as egrets or bitterns rather than herons. Members of the genus '' Botaurus'' are referred to as ...

found across South America. It has predominantly pale grey plumage with a darker grey crest. A carnivore, it hunts fish and crustaceans in shallow water.

Taxonomy and evolution

The cocoi heron was originally described by

Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

in his 1766 12th edition of ''Systema Naturae'', The origin of its species name is unknown, but may be related to the common name in Chile ''cuca'', which in turn denotes the bird's call note.Johnson AW. 1965. The Birds of Chile. Privately printed, Buenos Aires. It is more widely known in South America as ''garza mora'' or "black heron".Hancock J, Kushlan J. 1984. ''The Herons Handbook''. Croom Helm, 1st edition. The cocoi heron forms a

superspecies In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

with the similar Afro-Eurasian

grey heron The grey heron (''Ardea cinerea'') is a long-legged wading bird of the heron family, Ardeidae, native throughout temperate Europe and Asia, and also parts of Africa. It is resident in much of its range, but some populations from the more norther ...

and North and Central American

great blue heron The great blue heron (''Ardea herodias'') is a large wading bird in the heron family Ardeidae, common near the shores of open water and in wetlands over most of North and Central America, as well as far northwestern South America, the Caribbea ...

, with all of these species showing similar skeletal

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

Description

The cocoi heron is the largest of the South American heron species and measures in length,Dunning Jr. JB. 2008. CRC Handbook of Avian Body Masses 2nd Edition. Florida: CRC Press.Blake ER. 1977. Manual of Neotropical Birds, Vol I. Chicago. although body sizes vary regionally; with southern individuals probably being the largest. Adult weight of both males and females can variously range from . In the adult, wing length has been recorded as , tail length , culmen from base and tarsus . Sizes are similar to its North American counterpart, the

, although the latter may average slightly larger. The sexes are alike in both body size and colouration. It has a grey back and upper wings and a white S-shaped neck, thighs, under-tail wing coverts and

scapulars The scapula (: scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on either side ...

; with black streaks on the neck and upper breast. The forehead and crown of the head are black and this black extends down to the eye region and up to the pointed crest hanging down the nape. There is also black streaking on the neck and black patches on sides of the lower breast and abdomen. Leg colour has been reported as black, brownish-grey or dark green. The iris is usually yellow and the bill dull yellow. The bare skin of the orbital region is pale greenish. Some breeding cocoi herons observed in Argentina have bright yellow bills with a red tinge at the base and dusky pink legs. In flight, its large wings make it a slow but sturdy and graceful flyer. The voice is a deep croak.Kushlan JA. 2011. The terminology of courtship, nesting, feeding and maintenance in herons. Heron Conservation. Overall, the cocoi heron is similar in appearance to the grey heron; but the former has slightly darker colouration and a longer neck and crest. In the juvenile, the underparts are ash grey and streaked with buff. The neck and upper body surface are pale brownish with a little ash grey tinge on the neck. Compared to the adult, the crown is duller and the under-tail coverts have a dusky streaking. Juveniles also lack the long plumes and occipital crest typical of the adult. Despite the paler colouration, the downy chick already shows the contrast between the dark head and pale neck typical of the adult.

Similar species

At the northernmost extent of its range (e.g.,

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

and

Panama Panama, officially the Republic of Panama, is a country in Latin America at the southern end of Central America, bordering South America. It is bordered by Costa Rica to the west, Colombia to the southeast, the Caribbean Sea to the north, and ...

), the cocoi heron sometimes overlaps in range with the closely related and similarly sized

(''A. herodias''). The cocoi is distinguished by a striking white neck and solid black crown, but the duller juveniles are more easily confused.

Distribution and habitat

The cocoi heron occurs throughout much of South America except in the

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

and in some parts of

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 ...

.Ducommun M de la Paz, Beltzer AH. 2010. Feeding ecology of Cocoi Heron (''Ardea cocoi'') in the flood valley of the Parana River. Avian Biology Research 3 (3): 115-121. It is native in Argentina,

Suriname Suriname, officially the Republic of Suriname, is a country in northern South America, also considered as part of the Caribbean and the West Indies. It is a developing country with a Human Development Index, high level of human development; i ...

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

Bolivia Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features diverse geography, including vast Amazonian plains, tropical lowlands, mountains, the Gran Chaco Province, w ...

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 ...

Ecuador Ecuador, officially the Republic of Ecuador, is a country in northwestern South America, bordered by Colombia on the north, Peru on the east and south, and the Pacific Ocean on the west. It also includes the Galápagos Province which contain ...

French Guiana French Guiana, or Guyane in French, is an Overseas departments and regions of France, overseas department and region of France located on the northern coast of South America in the Guianas and the West Indies. Bordered by Suriname to the west ...

Guyana Guyana, officially the Co-operative Republic of Guyana, is a country on the northern coast of South America, part of the historic British West Indies. entry "Guyana" Georgetown, Guyana, Georgetown is the capital of Guyana and is also the co ...

Paraguay Paraguay, officially the Republic of Paraguay, is a landlocked country in South America. It is bordered by Argentina to the Argentina–Paraguay border, south and southwest, Brazil to the Brazil–Paraguay border, east and northeast, and Boli ...

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

and

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 ...

. Overall, the cocoi heron is notably widespread and ranges from Central America to the mainland shores on the

Strait 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 natura ...

, but is rarely found further south than

Chubut Chubut may refer to: * Chubut Province Chubut ( from Tehuelche language, Tehuelche 'transparent'; ) is a provinces of Argentina, province in southern Argentina, situated between the 42nd parallel south (the border with Río Negro Province), ...

in Argentina. It has an estimated extent of occurrence of 20600000 km². It inhabits the wetter parts of the ChacoShort LL. 1975. A zoogeographic analysis of the South American Chaco avifauna. Bulletin of the American Museum of Natural History 154: 163-352. and occurs as a vagrant in the Falkland Islands,Woods RW. 1975. The Birds of the Falkland Islands. Anthony Nelson, Oswestry. Saint Helena,

Ascension Island Ascension Island is an isolated volcanic island, 7°56′ south of the Equator in the Atlantic Ocean, South Atlantic Ocean. It is about from the coast of Africa and from the coast of South America. It is governed as part of the British Overs ...

and

Tristan da Cunha Tristan da Cunha (), colloquially Tristan, is a remote group of volcano, volcanic islands in the South Atlantic Ocean. It is one of three constituent parts of the British Overseas Territories, British Overseas Territory of Saint Helena, Ascensi ...

. It is a regular, non-breeding visitor to Trinidad and Tobago.Barran S. 2017. The online guide to the animals of Trinidad and Tobago, ''Ardea cocoi'' (Cocoi heron or white-necked heron). UWI Ecology. The habitat comprises almost any body of water or wetland away from dense forest; including lake shores, swamps, rivers and estuaries. Gallery forest, grassland and beaches have also been reported to be suitable feeding grounds. Pastures appear to be disfavoured probably because these habitats harbour a large proportion of insects, which are less favoured as prey than fish and mammals. In 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 ...

, the habitat appears to comprise small streams. In one study in the

Parana river Paraná, Paranã or Parana may refer to: Geology *Paraná Basin, a sedimentary basin in South America Places In Argentina *Paraná, Entre Ríos, a city * Paraná Department, a part of Entre Ríos Province In Brazil *Paraná (state), a state ...

, water with aquatic vegetation was found to be the most preferable, followed by open waters, with the lowest preference for beaches. This heron is found at elevations up to 2550 m above sea level.

Ecology

Feeding

This heron feeds primarily on fish measuring over long; with mammals, amphibians and sometimes insects also being consumed. Fish species consumed include whitemouth croaker,Faria FA, Silva-Costa A, Gianuca D, Bugoni L. 2015. Cocoi heron (''Ardea cocoi'') connects estuarine, coastal, limnetic and terrestrial environments: an assessment based on conventional dietary and stable isotope analysis. Estuaries and Coasts 39.4: 1271-1281. wolf fish, various ''

Leporinus ''Leporinus'' is a genus of fish in the family (biology), family Anostomidae native to South America. The fossil species ''Leporinus scalabrinii'', known from the late Miocene of Entre Ríos Province, Entre Ríos in Argentina, has only recently b ...

'' species up to 200 mm long and streaked prochilod.Borrero JI, Cruz-Millan CA. 1982. Notas sobre la historia de la garz morena ''Ardea cocoi'' (Aves) en Colombia. Acta Biológica Colombiana 1: 51-75. This heron has also been observed to feed on carrion and '' Callinectes'' blue crabs. In Colombia, chicks have also been observed being fed predominantly fish and less frequently with amphibians and crustaceans. The cocoi heron catches prey by striking its head into the water and thrusting its bill to stab downwards. It may also tilt its head downward above the water so that only its bill is immersed. During feeding, the head and neck move rapidly while the body remains immobile. Feeding is usually diurnal and solitary, especially in Argentina, although in Chile, it is considered to be a largely nocturnal feeder, with diurnal roosting taking place in trees overlooking the water. In Venezuela, it has also been seen foraging in large groups. Where feeding is diurnal, there appears to be a peak in feeding activity at noon and a reduction at dusk. The cocoi heron appears able to use alternative food sources by exploring foraging sites distant from its breeding colonies, since terrestrial rodents and reptiles and marine organisms have been found in the diet of individuals from freshwater colonies. Some colonies also reside near to estuarine coastland and individuals from these colonies are more reliant on marine prey. Foraging individuals often stay near to colonies and colony site choice has been found to be strongly linked to proximity to high-quality foraging habitats. The heron may also sometimes exploit dead whitemouth croaker discarded by recreational fisheries.

Breeding

Generation length in years has been estimated as 10.5 years, with a maximum longevity of 24.4 years. This heron is primarily non-migratory, but may move toward the equator during winter to seek warmer temperatures. The onset of the nesting season varies geographically. In Suriname, it begins in July; whereas it begins in August to November in Brazil and Argentina,Wildscreen 2017. Cocoi heron. http://arkive.org/cocoi-heron/ardea-cocoi/ . October in Uruguay and November in the Buenos Aires region. The cocoi heron nests colonially in trees. The large, deep nest is constructed from branches and sticks with grass, usually situated in trees. Near Buenos Aires, nests consisted of branches of ''Solanum glauca'' and dry thistles. They were roughly circular, 65 cm in diameter and very deep. In Chile, cocoi herons have been observed to construct their nests on weeping willow trees in standing water with rushes. The eggs are pale blue with paler speckles and some whitish traces. Egg dimensions from various clutches in South America lie in the range 62-69 x 45–48 mm. Eggs from one Argentinian clutch weighed 70-80 g. From one colony in

Buenos Aires Buenos Aires, controlled by the government of the Autonomous City of Buenos Aires, is the Capital city, capital and largest city of Argentina. It is located on the southwest of the Río de la Plata. Buenos Aires is classified as an Alpha− glob ...

, incubation was estimated as 24–26 days. However, in one Chilean colony where eggs hatched in September (spring), incubation period was estimated as 27 days, ranging 26–29 days.Gonzalez-Acuna D, Figueroa RA, Gonzalez A, Barrientos C, Ardiles K, Moreno L. 2008. Biologia reproductiva de la garza cuca (''Ardea cocoi'') en el centro-sur de Chile. Ornitologia Neotropical 19: 485 – 493. Clutch size is 1 to 4 eggs. Juveniles may remain in the nest for up to 12 to 13 weeks, but most leave at 6 to 7 weeks.

Threats

Alongside human inference, one natural threat may be posed by

crested caracara The crested caracara (''Caracara plancus'') is a bird of prey (raptor) in the falcon Family (biology), family, Falconidae. It was formerly placed in the genus ''Polyborus'' before being given in its own genus, ''Caracara (genus), Caracara''. It i ...

. In a colony in

, the young in a caracara nest hatched before that of the cocoi heron in a nearby nest. The former were reared largely on the heron chicks.

Conservation

The cocoi heron is classified by 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 ...

least concern A least-concern species is a species that has been evaluated and categorized by the International Union for Conservation of Nature (IUCN) as not being a focus of wildlife conservation because the specific species is still plentiful in the wil ...

because of its extensive geographical range, apparently stable population trend and large population size. Individuals in some territories are affected by agrochemicals, environmental modification and human interference with nests and eggs, but these issues do not constitute severely harmful threats and do not threaten the species with extinction.

References

{{Taxonbar , from=Q911449

cocoi heron The cocoi heron (''Ardea cocoi'') is a species of long-legged wading bird in the heron family Ardeidae found across South America. It has predominantly pale grey plumage with a darker grey crest. A carnivore, it hunts fish and crustaceans in sha ...

Birds of South America

Taxonomy articles created by Polbot