Cocoi Heron Identification Guide

Key Field Marks

• Size & shape: A very large heron (95-127 cm) with the classic long-legged, long-necked, dagger-billed heron silhouette; among the largest herons in the Americas.
• Head & neck: Gleaming white crown and face bordered by a black cap that extends into long black plumes trailing off the back of the head; the foreneck is white, often with fine dark streaking down the front.
• Body: Blue-gray back and wings, with contrasting black flanks and thighs and a whitish belly — a much more strongly patterned, higher-contrast look than the more uniformly gray Great Blue Heron.
• Bill & legs: Long, heavy, yellowish bill (duskier at the tip in some individuals) and long grayish-black legs.
• Behavior: A patient, solitary stand-and-wait hunter along water edges, spearing fish, amphibians, and other prey with a rapid strike; often seen standing motionless in shallow water or flying with slow, deep wingbeats and a folded S-shaped neck typical of herons.

Separating It From Similar Species

• Great Blue Heron: Cocoi Heron is essentially the South American ecological equivalent, but shows a cleaner white face/foreneck, more sharply defined black cap and flanks, and an overall crisper black-and-white-and-gray pattern versus the more uniformly grayish-brown, less contrasty Great Blue Heron (rare as a vagrant/winterer in northern South America but generally allopatric).
• Whistling Heron: Much smaller, plumper, buffier overall, with a short thick bill and blue facial skin — a very different overall impression.
• Great Egret: All white, with no gray body or black cap, and a more slender build.

Habitat, Range & Season

• Widespread and common throughout most of South America, from Colombia and Venezuela south to Tierra del Fuego, and on the Galápagos and other offshore islands.
• Found in a wide range of wetland habitats: rivers, lake edges, marshes, mangroves, flooded fields, estuaries, and coastal mudflats, from lowlands well up into montane wetlands.
• Largely resident, though some local or altitudinal movements occur in response to water levels and season.

Voice

• Gives deep, harsh croaking and guttural squawks, especially when flushed or at breeding colonies, generally similar in tone to other large herons.