Great Blue Heron

Ardea herodias

(c) Glen Tepke
  • ARDEIDAE
  • Herons, Bitterns, Egrets
  • Ciconiiformes
  • Garza morena, Garza blanca granda, Gallinaza
  • Grand héron
Introduction


 

Statuesque and graceful in movement, the Great Blue Heron is one of North America’s most familiar and adaptable wading birds. At four feet tall, with a six-foot wingspan, it is also the continent’s largest heron species. While vocal in flight, Great Blue Herons are frequently observed standing silent and motionless along shorelines. The bird takes to the sky with slow, deep wingbeats, its long neck curved into an S-shape, and its head hunched back upon its shoulders.

 

(c) Shawn Carey
Appearance Description

Slate gray, with a blue tinge that gives the bird its name, the Great Blue Heron has black shoulder patches, a white face, and a white crown that is underscored by black eye-stripes ending in slender plumes. Long plumes also extend from the slender, elongated body at the neck, breast, and back. The bird has a thick yellow bill and long, stilt-like brownish or greenish legs with chestnut thigh feathers. An all-white morph called the “Great White Heron,” formerly considered a separate species, lives in southern Florida, the Yucatan Peninsula, and the Caribbean. Where the ranges of these two forms overlap, interbreeding produces “Wurdemann’s herons,” which have the body coloration of a Great Blue and the head and neck plumage of a Great White. Weighing about five pounds, the Great Blue Heron measures four feet in height and has a six-foot wingspan. Both sexes are similar in appearance, with males being slightly larger.

Range Map
Courtesy Kenn Kaufman
Range Map Legend
Range Distribution
Widespread across North America, Great Blue Herons thrive year-round in both freshwater and saltwater habitats from southern Alaska to Central America, across much of the United States, and into the Caribbean Islands. During breeding season, they extend their northern range into central Canada and eastward to Nova Scotia. Colonies also nest on Ecuador’s Galapagos Islands. In winter, the species can be found as far south as the coastlines of Colombia and Venezuela.
 
A legend for the range map to the right can be found here.
 
Habitat

Great Blue Herons can be found in a wide variety of aquatic habitats, ranging from riverbanks, marshes, and swamps to tidal flats and shores. Feeding takes place mostly in still or slow-moving fresh or salt water, and occasionally along seacoasts and in fields. The birds typically nest in treetop colonies and bushes located in swamps, islands, peninsulas, and shorelines, and less frequently, upon the ground or artificial structures. Preferred nest sites are close to foraging areas and relatively difficult for humans and terrestrial predators to reach. In New York and New Hampshire, the birds avoid nesting in marine habitats, favoring inland sites instead.

Feeding
Although primarily fish eaters, Great Blue Herons have a varied diet that includes invertebrates, amphibians, reptiles, birds, insects, and small mammals, especially voles. Patient hunters, the birds forage night and day, usually alone, but sometimes in small groups. They hunt by slowly wading or standing still in shallow water until prey comes close enough to be caught with a rapid thrust of the bill.
Reproduction
Great Blue Herons breed in colonies containing a few to several hundred pairs; isolated pair breeding is rare. Soon after reaching their nesting grounds, the birds choose new mates for that year. Mating follows elaborate courtship displays. Nests are usually situated high up in trees. The male gathers sticks for the female, who fashions them into a platform nest. Clutches contain two to six pale blue eggs, which are incubated by both parents for 25 to 30 days. Both parents care for the chicks, which are fed by regurgitation. The young begin flying when they are about two months old, although they return to the nest to be fed by the adults for another few weeks.
Migration
There are both migratory and resident Great Blue Heron populations in North America. Pacific Coast populations are thought to be non-migratory. Migrants travel day and night, alone or in small groups. In summer, they may journey northward to the Alaskan Arctic, southern Yukon, and northern Manitoba, Ontario, and Quebec. They then migrate south from mid-September to late October. Most birds winter along ice-free coastlines and watercourses, with many migrating to Caribbean shores and the southeastern United States.
CBC Graph
Graph Legend
Annual Population Indices
  • Unknown
  • 124,500
  • no current conservation concerns
Population Status Trends
Early in the 20th century, Great Blue Herons suffered from unrestricted hunting, but today, with legal protection and greater awareness about conservation, they are among the most abundant wading birds in North America.
 
An explanation of the Annual Indices graph displayed to the right can be found here.
Conservation Issues
Great Blue Herons were impacted less by plume hunters and pesticides than other heron species, and their numbers have remained strong over a broad range. However, colonies are vulnerable to disturbance. The birds may abandon rookeries or experience diminished reproductive success when disrupted, especially early in the breeding season. Moreover, the destruction of wetland habitat is a serious threat. Clearcutting of forests and construction near heronries are also detrimental.
What You Can Do
Don’t disturb Great Blue Heron nesting sites or colonies when hiking or landing boats; the birds may abandon their nests or colonies. 
 
Great Blue Herons can be killed or injured when ensnared in fishing tackle. Don’t discard or abandon snagged fishing lines and lures.
 
Be alert to local, regional, and federal land management decisions, particularly those related to wetlands. Support protection of Great Blue Heron nesting sites, feeding grounds, and winter habitats. 
 
For actions you can take, including Audubon activities, please visit our resources page.
More Information
Visit our resources page for more information about this species.
Natural History References
Butler, R.W. 1992. Great Blue Heron. In The Birds of North America, No. 25 (A. Poole, P. Stettenheim, and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, DC: The American Ornithologists’ Union.
 
Kaufman, Kenn. Lives of North American Birds, Houghton Mifflin Company, New York, 1996.
 
Sibley, David Allen. The Sibley Guide to Birds. Alfred A. Knopf, New York, 2000.
Conservation Status References
Butler, R.W. 1992. Great Blue Heron. In The Birds of North America, No. 25 (A. Poole, P. Stettenheim, and F. Gill, Eds.). Philadelphia: The Academy of Natural Sciences; Washington, DC: The American Ornithologists’ Union.
 
Kaufman, Kenn. Lives of North American Birds, Houghton Mifflin Company, New York, 1996.
 
Sibley, David Allen. The Sibley Guide to Birds. Alfred A. Knopf, New York, 2000.