Great blue heron

Great blue heron, (Ardea herodias), well-known species of large North American herons, classified in the bird family Ardeidae in order Pelecaniformes, recognized for its blue-gray plumage and graceful, stately demeanor, its large size, and its wide wingspan—which extends up to nearly 2 meters (6.6 feet) or more. The species is the largest heron on the continent, and it occurs from Alaska, Canada, and the contiguous U.S. south to the islands of the Caribbean Sea, and Mexico to northern Colombia and Venezuela where many migratory individuals overwinter.

Most classifications divide great blue herons into four or five subspecies: A. herodias cognata (Galapagos Islands), A. herodias fannini (which lives along the Pacific coast from Washington to southeastern Alaska), A. herodias herodias (whose geographic range extends from southern Canada south through much of the western continental U.S. to Central America), A. herodias wardi (whose range spans the southeastern U.S.). Some classifications, however, consider great white herons (subspecies A. herodias occidentalis), whose range extends from southern Florida through the islands of the Caribbean Sea, to be a separate species.

Natural history

The species is recognized by its s-shaped neck and long stick-figure legs. Adult great blue herons stand almost 1.4 meters (4.6 feet) tall and weigh between 2.1 and 3.3 kg (4.6 and 7.3 pounds), with males being slightly larger and heavier than females. Great blue herons have gray-blue wings with white plumes of feathers, long necks that range in color from white to gray with patches of rust-red, black crowns, long legs, and yellowish pointed beaks.

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Great blue herons are primarily fish eaters that often feed near dawn and dusk. They also prey on rodents, insects, amphibians (such as frogs and salamanders), crustaceans, and even turtles or other birds. They capture their prey with their spear-like bill, striking their quarry suddenly before swallowing it whole. Adult great blue herons have few natural enemies. Though birds of prey (such as hawks, eagles, and turkey vultures), along with bears and raccoons, will occasionally prey on both adults and juveniles, raccoons, crows, ravens, as well as hawks and eagles, will eat great blue heron eggs. To increase their survivability, great blue herons build nests—some of which can reach up to 1.2 meters (4 feet) wide and 1 meter (about 3.5 feet) deep—in colonies called rookeries, usually in trees, small shrubs, and near the water’s edge. Although most heron rookeries are made up of 50 pairs, the largest heron rookeries can contain 500 or more birds. The species is largely migratory, with populations living in Canada and the northern U.S. flying south in the winter in search of open water, but populations living in the southern U.S. often remain in their nests year-round. They can fly 32–48 kilometers (20–30 miles) per hour.

The species breeds once per year, with breeding adults finding new mates each year. After an elaborate courtship that involves the male flexing his neck, fluffing his neck feathers, and flying around his potential nest site, a female great blue heron may join him to breed. After fertilization occurs, females will deposit between two and seven pale blue eggs in the nest. Both parents will take turns incubating the eggs before the eggs hatch some 25–30 days later. Young will fledge some 60 days after they hatch and go off on their own some 30 days later. Some sources note that older, stronger siblings may kill their smaller, weaker siblings, especially if food is in short supply. Surviving young reach sexual maturity at age 22 months, and they typically live for about 15 years; however, the oldest known great blue heron is thought to have lived 23 years in the wild.

Conservation status

Owing to the great blue heron’s large population size, adaptability, and vast geographic range, it is listed as a species of least concern by the International Union for Conservation of Nature and Natural Resources (IUCN). Great blue heron populations declined in the 19th century and early 20th century, when hunters shot them for their feathers to decorate hats, which were fashionable in Europe and the U.S. at the time. The Lacey Act, a 1900 environmental law, aided the great blue heron’s recovery by banning foreign and interstate trade of wildlife parts. The species is also protected by the Migratory Bird Treaty Act of 1918. Great blue heron populations in parts of eastern North America have increased in the wake of the recovery of beavers (Castor canadensis) in the region. These small mammals construct dams, which expand the number and size of marsh and wetland habitat that great blue herons use for nesting and foraging. In the present day, the number of mature great blue herons stands between 500,000 and 5 million birds.