When the heron takes to flight, what a change in size and appearance! ....There go two great undulating wings pinned together, but the body and neck must have been left behind somewhere.      Thoreau on Birds*

Ardea herodias, the great blue heron, stands four feet tall and has a wingspan of more than six feet. It is the largest and most widely distributed of the North American herons, and dwarfs its closest relatives, including egrets, bitterns and other herons.

Despite its size, the great blue heron weighs only about 6.5 pounds when fully grown. It is a relatively quiet bird that spends ninety percent of its waking hours foraging for food. In both sexes the body is a dark blue-gray, which contrasts with its white-streaked black breast and abdomen. Its long neck is also gray, and it has a white crown, cheeks and throat. Two long, black occipital crests rise from the crown stripe in adult herons. Like other herons, the great blue has a short, blunt tail, extremely long legs, a long neck and a sharp bill.

The great blue heron hunts in protected, shallow coves in the Chesapeake Bay and its tributaries. Its primary diet consists of small fish, which it swallows head first, and frogs, salamanders, snakes, lizards, shellfish, small birds, rodents, dragonflies, grasshoppers and many aquatic insects. The heron wades stealthily through the shallows, and freezes for a few moments before its strikes at its prey with its dagger-like bill. The great blue heron is one of the top predators of the Bay food chain.

• Most herons breed in localized colonies, often called "rookeries," of sometimes hundreds of nesting pairs. Occasionally herons nest singly.
• Herons form pair-bonds in early spring, in March and April, after courtship rituals that involve both sexes.
• The male heron may build a new nest or revitalize one that survived the winter. Nest sites are usually in living, but occasionally dead, trees and bushes. They seem to prefer loblolly pine, beech and oak, and large sycamores, where they build rickety nests of sticks sometimes lined with grass, reeds and moss. Most are situated high in the tree canopy, safe from predators on the ground.
• The female heron lays three to seven eggs in March and April. Both parents care for the eggs during the 28-day incubation period, after which both feed regurgitated fish to the newly hatched nestlings.
• Although herons lay several eggs, they usually raise only one or two; the others starve after hatching. After about 60 days, the young fledge and leave the nest.

Because herons often congregate in nesting rookeries, scientists are able to count the number of herons that inhabit the Bay region each year. Some rookeries are exceptionally large and are important preservation sites. The Bay provides ideal food and habitat for the blue heron’s survival. In 1990 surveys found 4,600 nesting pairs of great blue herons in more than 38 colonies in Maryland. At the Nanjemoy Creek Sanctuary near the Potomac River, volunteers counted more than 1,300 nests in that year. The area is under the stewardship of the Nature Conservancy.

Herons have not always been so well protected. In the late 19th and early 20th centuries, hunters shot herons, egrets and other birds with flamboyant plumage to collect their feathers for the millinery industry, and others shot the birds merely for sport. The heron was saved from extinction by the federal government’s passage of the Lacey Act, which forbids foreign and interstate trade of wildlife parts, and the Migratory Bird Treaty Act of 1918.

Although herons have adapted well to the presence of humans and shoreline development, their nesting colonies remain vulnerable to human encroachment. Herons often build their rookeries on islands that are eroding and use swamps for nesting, which may be drained for agricultural purposes. With the destruction of Bay wetlands, the heron is threatened with the loss of valuable nesting and feeding grounds, and the deterioration of Bay water quality reduces the quantity of available prey.

* - Thoreau, Henry David.  1998.  Thoreau on Birds. 510 pp.  Beacon Press, Boston.

Image courtesy: U.S. Fish and Wildlife Service

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Last modified: 12/11/03