The Green heron is a small solitary heron that lives along shaded riverbanks or quiet streams in areas of dense vegetation. It is often somewhat secretive but is sometimes to be seen crying "kyow" while flying up a creek. When in the open, it will often flick its short tail nervously, while raising and lowering its crest. The "green" of its back is an iridescence, and often appears as a dull blue or just dark.
Green herons come from the Americas and occur in North America, Central America, and the Caribbean. They breed in the Pacific states of the U.S. and the extreme south east of Canada, Central Panama, the West Indies and the islands off Venezuela’s north coast. Being a partially migratory species, the most northerly populations migrate before winter to the southern U.S., northern Colombia, eastern Ecuador and northern Venezuela. It is a very adaptable wetland bird and will occupy almost any shallow water habitat within its geographical range. It is often found in swampy thickets, as it prefers to forage amongst dense vegetation, but when food is available it may feed out in the open.
Although they are quite common, Green herons are shy and so are not often observed. Their active period is during the day and they nest within their feeding areas. To catch fish they either stand in the water or perch low above the water, watching for prey, or they track it down. Occasionally they will swim after prey. They will retract their neck, holding their bill downwards aiming at a fish, take a few cautious steps and stab their prey with their bill. They feed either alone or as a pair. When threatened, alarmed or aggressive, Green herons raise their crest, hold their neck still and flutter their tail. They are territorial and do not tolerate intrusions. They attack intruders on sight, flying towards them, making a loud and guttural repetitive "annnck-annnnck". This call is also repeated as an alarm.
Green herons are carnivores (piscivores and insectivores), they eat fish, insects, amphibians, crayfish, invertebrates, earthworms, leeches, dragonflies, grasshoppers, small rodents, lizards, snakes, frogs and tadpoles.
Green herons are serially monogamous, which means they mate with only one partner in a breeding season. The courtship display by the male is a circular flight similar to natural flight, but is directed towards the bird’s breeding area and accompanied by calls. The breeding season varies considerably in different geographic areas, generally beginning any time from March until July. Green herons nest either alone or in a loose groups. The male will protect the nest site during the construction of the nest. A pair builds a platform of sticks and stems, in trees or bushes, above or near water. 2 to 4 eggs are laid and incubation is by both parents, for about 21 to 25 days. The parents feed regurgitated food to the chicks, which begin hopping around their nest, snapping at insects after about 16 to 17 days when they are fledged. They gain independence at around 30 to 35 days. Chicks are dependent on their parents for about another month after fledging, reaching maturity at one year old.
The Green heron used to be persecuted because it would forage at fish hatcheries; this may still happen today to some extent. It is possibly also possibly under threat due to the alteration of wetlands, as this can reduce breeding and foraging habitat. Further threats are contamination from pesticides, as well as disturbance from people using rivers for recreation.
The Green heron is common and widespread throughout its range but no overall population estimate is available. Currently this species is classified as Least Concern (LC) on the IUCN Red List, however, its numbers today are decreasing.
Green herons have an important role in their aquatic habitat as predators of fish and invertebrates, controlling these populations.