Cocoi Heron

The Cocoi Heron, Ardea cocoi, stands as the largest heron species gracing the South American landscape. This majestic bird exhibits a predominantly pale grey plumage, accented by a darker grey crest, and a striking white S-shaped neck. The sexes are indistinguishable in size and coloration, both adorned with black streaks along the neck and upper breast, and a black crown that extends to the eye region and culminates in a pointed crest draping down the nape. The legs may present as black, brownish-grey, or dark green, while the iris typically shines a bright yellow, complementing the dull yellow bill.

Identification Tips

Adult Cocoi Herons measure between 95 to 130 cm in length, with a wingspan that supports their slow, yet stable and graceful flight. The bare skin around the eye is a pale greenish hue, and during the breeding season, some individuals may boast a bill tinged with red at the base and dusky pink legs. Juveniles, in contrast, display ash grey underparts with buff streaks and a paler brownish upper body, lacking the adult's long plumes and occipital crest.

Habitat

The Cocoi Heron favors a variety of wetland habitats away from dense forests, including lake shores, swamps, rivers, estuaries, gallery forests, grasslands, and beaches. It is adept at finding sustenance in these environments, which range up to 2550 meters above sea level.

Distribution

This heron's domain stretches across much of South America, from Central America to the mainland shores of the Strait of Magellan. It is notably absent from the Andes and some parts of Argentina. The species is also a regular, non-breeding visitor to Trinidad and Tobago and has been recorded as a vagrant in the Falkland Islands and other remote Atlantic locales.

Behaviour

The Cocoi Heron is primarily a solitary feeder, hunting by day, particularly in Argentina. However, in some regions like Chile, it adopts a nocturnal feeding pattern. It is known to forage in large groups in Venezuela. This heron is primarily non-migratory but may relocate towards the equator during winter months.

Song & Calls

The Cocoi Heron communicates with a deep, resonant croak, which is characteristic of its kind.

Breeding

Breeding seasons vary geographically, with nesting commencing from July to November, depending on the location. These herons nest colonially in trees, constructing large, deep nests from branches and sticks. Clutch sizes range from 1 to 4 pale blue, speckled eggs, with incubation periods estimated between 24 to 29 days.

Similar Species

In the southernmost parts of its range, the Cocoi Heron may be confused with the great blue heron, especially the juveniles. However, the Cocoi Heron can be distinguished by its white neck and solid black crown.

Diet and Feeding

A carnivorous bird, the Cocoi Heron preys on fish over 20 cm long, mammals, amphibians, and occasionally insects. It employs a striking motion to catch prey, thrusting its bill into the water with precision. It has also been observed feeding on carrion and exploiting alternative food sources, such as terrestrial rodents, reptiles, and marine organisms.

Conservation status

The IUCN classifies the Cocoi Heron as Least Concern, acknowledging its extensive range, stable population trend, and robust numbers. While some individuals face challenges from agrochemicals, habitat modification, and human disturbance, these threats are not currently severe enough to imperil the species.