Cocoi Heron

The Cocoi Heron is the largest heron in South America and the continent's ecological equivalent of the Old World Grey Heron. It has a pale grey back and wings, a white neck and underparts, and a bold black cap that extends into a black stripe running down the side of the neck. The legs are long and dark, and the bill is heavy, yellowish, and dagger-shaped.

Standing up to 1.3 metres tall, it is an unmistakable, statuesque presence along South American waterways, often seen standing alone at the water's edge or flying with slow, deliberate wingbeats and its neck tucked into an S-shape.

Key field marks

• Large size with pale grey back and white head, neck, and underparts
• Black cap extending down the side of the neck as a dark stripe
• Long, heavy yellowish bill
• Long dark legs

Similar species

The Great Blue Heron, which occurs in parts of northern South America during migration, is similar but shows more chestnut and slaty tones with rufous thighs, whereas the Cocoi Heron is cleaner grey and white. Immature Cocoi Herons are duller and browner but retain the overall pattern and large size.

Habitat

Cocoi Herons use a wide range of wetland habitats, including rivers, lakes, marshes, flooded grasslands, and coastal estuaries, from lowlands up to high Andean lakes.

Range and migration

The species is distributed throughout South America, from Colombia and Venezuela south to Tierra del Fuego, and is mostly resident, though some southern populations shift northward outside the breeding season.

Behavior

Typically solitary while foraging, Cocoi Herons stand and wait or wade slowly through shallow water, striking prey with a rapid jab of the bill. They are wary and will fly off with a loud call when disturbed.

Voice

A harsh, croaking squawk similar to other large Ardea herons, given especially in flight or when alarmed.

Feeding

Fish form the bulk of the diet, supplemented by frogs, small mammals, and large insects caught in shallow water or open grassland.

Nesting and breeding

Cocoi Herons nest in colonies, often alongside other waterbirds, building stick nests high in trees; clutches usually contain 2-4 eggs.