The South American counterpart of North America’s great blue heron, Cocoi herons are long-legged wading birds, found in a range of wetland landscapes across the continent. They are carnivorous, foraging for large fish and crustaceans in shallow water.
A large gray heron, the Cocoi heron has some distinguishing markings that make it easy to identify when compared to similar wading birds in the field.
Their upperparts are mainly gray, with a black forecrown that extends to below the eye, and a black crest that reaches down the back of their neck. Their gray wings feature a black shoulder patch, and additionally, patches of black are present on the thigh and lower belly. The breast and underparts are white, with the upper breast streaked with black markings.
Cocoi herons have yellow eyes, with a patch of blue exposed scaly skin at the base of the bill. The bill itself is a dull yellow, becoming brighter in the breeding season. Legs and feet are black, changing to a grayish-pink when breeding.
Male and female Cocoi herons are alike in both size and plumage.
Juvenile Cocoi herons are grayer than adults, particularly on the neck. Buff-colored streaks are visible across their underparts, their crown is a duller black and they do not have the long crest at the rear of the crown.
Cocoi Heron perching in a tree along the riverbank
Cocoi herons are the largest heron species in South America and are usually slightly larger than North America’s great blue heron. There is usually no great difference in size between males and females, and birds living in the southern part of the range are generally larger than those further north.
Cocoi Heron in-flight over natural habitat
At roosting sites and nesting colonies, the guttural calls of Cocoi Heron can be heard, that sound like ‘rraahbm rraabb’. In flight, a series of “gawk uk, guk uk, guk uck uck” cries may be made.
Cocoi Heron perched on a large branch calling
The Cocoi heron’s diet primarily consists of large fish, up to 30 cm (12 in) in length, but they also eat frogs, aquatic insects, and their larvae, crabs, and carrion. Small rodents, lizards, and young birds are also eaten.
Cocoi herons forage by standing in shallow water, watching for prey, and then stabbing quickly downwards with their bill, using a head-tilting technique to aid their view.
While in the nest, Cocoi heron chicks are fed on a broad diet, which includes fish, rodents, amphibians, crustaceans, spiders, beetles, and other insects. Occasionally, other baby birds may also be fed to nestlings.
Cocoi Heron catching its prey
Residents of natural wetland habitats, Cocoi herons are found in freshwater and saltwater environments, in swamps, woodlands, grasslands, and estuaries. Riverbanks, lake shores, streams, and marshlands offer suitable foraging grounds, and the species are most commonly found in lowland landscapes, at altitudes lower than 2500 m (8000 ft).
Cocoi herons are present throughout South America, with the exception of the length of the Andes. The species is resident from Panama in the north, to the southern tip of Argentina, as well as on the northwest coast of Peru and the extreme west coast of Chile.
They are generally sedentary birds, although occasional post-breeding dispersal may occasionally lead to vagrant individuals turning up as far afield as Trinidad, Tobago, and the Falkland Islands.
Cocoi herons are native to South America and are found in Argentina, Panama, Suriname, Colombia, Venezuela, Bolivia, Brazil, Chile, Ecuador, French Guiana, Guyana, Paraguay, Peru, and Uruguay. The southern and central parts of the continent have the highest concentrations.
Cocoi Heron standing in a shallow marsh
In parts of South America, Cocoi herons are considered widespread and common, particularly in the south. In Panama the species is common, but there is no evidence of breeding.
Sightings become rarer along the north-eastern coast of Brazil, and Cocoi herons are scarce-to-absent on the coasts of Ecuador and Chile. Only the roughest population estimates are available, with the number of adult individuals estimated at between 5 and 50 million.
Frequent sightings of Cocoi herons are reported along riverbanks and shallow waters of Brazil’s Pantanal region. As one of South America’s most common herons, Cocoi herons can be spotted in many wetlands, marshes, and grassy swamplands across the continent.
Cocoi Heron in-flight over wetlands with prey in its beak
The average lifespan of a Cocoi heron is thought to be around 10.5 years, with the longest-lived individual recorded at 24.4 years of age.
Anaconda, caiman, and big cats may raid reedbed nests of Cocoi herons, while Southern caracara may prey on nestlings and young birds.
In the wild, Cocoi herons are protected under various conservation acts throughout South America. Extensive areas of their wetland habitats are included in the Ramsar Convention, which effectively safeguards the long-term survival of the species.
Cocoi herons have a wide geographical range and a stable population and are currently classified as a species of least concern globally.
Cocoi Heron walking in wetland habitat
Nests are generally built in either trees, bushes (including cacti), or in reedbeds. Cocoi herons are often colonial nesters but may also nest individually.
Deep, bulky cup-shaped nests are constructed from sticks, twigs, and reeds over the course of a week. A lining of grass is added before eggs are laid. Tree nests are most commonly found at a height of between 20 and 25 m (65 ft to 80 ft), with reedbed nest sites naturally lower down.
The breeding season for Cocoi herons varies according to geographical location. In Suriname, breeding begins in July, while in Brazil and Argentina, nesting occurs between August and November, and in Uruguay, October is typical.
The incubation period lasts from between 26 and 29 days and is shared between males and females.
Between 2 and 5 pale blue eggs are laid by Cocoi herons. Eggs, which measure on average 65 mm by 45 mm (2.6 in by 1.8 in), are speckled with lighter markings.
Little research is available, but observations indicate that Cocoi herons are monogamous for the duration of the breeding season, raising one brood together each year before separating once breeding is complete. A new mate is found the following year.
Cocoi Heron at nest with its young
Some aggressive displays may be witnessed when Cocoi herons are defending a territory or nest site. However, they are frequently seen to feed in large groups numbering up to 200 herons without conflict.
Most Cocoi herons are diurnal, feeding during daylight hours and roosting overnight in waterside trees. However, in Chile, populations of Cocoi herons are observed to feed nocturnally.
Cocoi Heron resting on a mangrove tree
Cocoi herons are typically a sedentary species, remaining in the same territories all year round. Brief periods of dispersal may occur after breeding and in the far southern extremes of their geographical range, some migration north may take place when local conditions become too inhospitable for survival.
Family:Herons, storks and ibises
95cm to 127cm
1.9kg to 2.1kg
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