Green herons are small and stocky, with legs that are relatively short, compared to other herons. Body length ranges from 41 to 46 cm. Adults have a glossy greenish-black cap and back, wings that are black grading into green and/or blue on the edges, and underparts that are gray. The bill is dark with a long, sharp point and the legs are orange. Female adults tend to be smaller, with duller and lighter plumage than that seen in males, particularly in the breeding season.

Coloration of immature herons is different. The neck and chest are striped with white and shades of brown. The back is also brown with white and beige spots. The coloration of immature and adult birds is quite cryptic in dense vegetation. (Hancock and Kushlan, 1984; Davis and Kushlan, 1994)

Range length: 41 to 46 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger; male more colorful

Average mass: 175 g.