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Great Blue Heron

Ardea herodias ORDER: PELECANIFORMES FAMILY: ARDEIDAE

IUCN Conservation Status: Least Concern

Whether poised at a river bend or cruising the coastline with slow, deep wingbeats, the Great Blue Heron is a majestic sight. This stately heron with its subtle blue-gray plumage often stands motionless as it scans for prey or wades belly deep with long, deliberate steps. They may move slowly, but Great Blue Herons can strike like lightning to grab a fish or snap up a gopher. In flight, look for this widespread heron’s tucked-in neck and long legs trailing out behind.

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At a GlanceHelp

Measurements
Both Sexes
Length
38.2–53.9 in
97–137 cm
Wingspan
65.7–79.1 in
167–201 cm
Weight
74.1–88.2 oz
2100–2500 g
Relative Size
Taller and much heavier than a Great Egret; smaller and much less bulky than a Sandhill Crane.
Other Names
  • Grande Héron (French)
  • Garza morena, Garza blanca granda, Gallinaza (Spanish)

Cool Facts

  • Thanks to specially shaped neck vertebrae, Great Blue Herons can curl their neck into an S shape for a more aerodynamic flight profile and to quickly strike prey at a distance.
  • Great Blue Herons have specialized feathers on their chest that continually grow and fray. The herons comb this “powder down” with a fringed claw on their middle toes, using the down like a washcloth to remove fish slime and other oils from their feathers as they preen. Applying the powder to their underparts protects their feathers against the slime and oils of swamps.
  • Great Blue Herons can hunt day and night thanks to a high percentage of rod-type photoreceptors in their eyes that improve their night vision.
  • Despite their impressive size, Great Blue Herons weigh only 5 to 6 pounds thanks in part to their hollow bones—a feature all birds share.
  • Great Blue Herons in the northeastern U.S. and southern Canada have benefited from the recovery of beaver populations, which have created a patchwork of swamps and meadows well-suited to foraging and nesting.
  • Along the Pacific coast, it’s not unusual to see a Great Blue Heron poised atop a floating bed of kelp waiting for a meal to swim by.
  • The white form of the Great Blue Heron, known as the "great white heron," is found nearly exclusively in shallow marine waters along the coast of very southern Florida, the Yucatan Peninsula, and in the Caribbean. Where the dark and white forms overlap in Florida, intermediate birds known as "Wurdemann's herons" can be found. They have the body of a Great Blue Heron, but the white head and neck of the great white heron.
  • The oldest Great Blue Heron, based on banding recovery, was 24 years old.
  • Great Blue Herons congregate at fish hatcheries, creating potential problems for the fish farmers. A study found that herons ate mostly diseased fish that would have died shortly anyway. Sick fish spent more time near the surface of the water where they were more vulnerable to the herons.

Habitat


Marsh

Great Blue Herons live in both freshwater and saltwater habitats, and also forage in grasslands and agricultural fields, where they stalk frogs and mammals. Most breeding colonies are located within 2 to 4 miles of feeding areas, often in isolated swamps or on islands, and near lakes and ponds bordered by forests.

Food


Fish

Great Blue Herons eat nearly anything within striking distance, including fish, amphibians, reptiles, small mammals, insects, and other birds. They grab smaller prey in their strong mandibles or use their dagger-like bills to impale larger fish, often shaking them to break or relax the sharp spines before gulping them down.

Nesting

Nesting Facts
Clutch Size
2–6 eggs
Number of Broods
1-2 broods
Egg Length
2.4–3 in
6.1–7.6 cm
Egg Width
1.8–2 in
4.5–5 cm
Incubation Period
27–29 days
Nestling Period
49–81 days
Egg Description
Pale blue, fading slightly with age.
Condition at Hatching
Bluish eyes open, chick covered in pale gray down, able to vocalize.
Nest Description

Male Great Blue Herons collect much of the nest material, gathering sticks from the ground and nearby shrubs and trees, and from unguarded and abandoned nests, and presenting them to the female. She weaves a platform and a saucer-shaped nest cup, lining it with pine needles, moss, reeds, dry grass, mangrove leaves, or small twigs. Nest building can take from 3 days up to 2 weeks; the finished nest can range from a simple platform measuring 20 inches across to more elaborate structures used over multiple years, reaching 4 feet across and nearly 3.5 feet deep. Ground-nesting herons use vegetation such as salt grass to form the nest.

Nest Placement

Tree

Great Blue Herons nest mainly in trees, but will also nest on the ground, on bushes, in mangroves, and on structures such as duck blinds, channel markers, or artificial nest platforms. Males arrive at the colony and settle on nest sites; from there, they court passing females. Colonies can consist of 500 or more individual nests, with multiple nests per tree built 100 or more feet off the ground.

Behavior


Stalking

Great Blue Herons forage, usually alone, across much of the U.S. This largest of the North American herons wades slowly or stands stock still, peering into the water for prey. In flight the Great Blue Heron folds it neck into an “S” shape and trails its long legs behind, dangling them as it prepares to land or when courting. Breeding birds nest in colonies that can number several hundred pairs, where they build stick nests in trees, on bushes, or on the ground. If you visit a colony, look for elaborate courtship and pair-bonding displays that include a ritualized greeting, stick transfers, and nest relief ceremony in which the birds erect their plumes and “clapper” their bill tips. Pairs are mostly monogamous during a season, but they choose new partners each year. Away from the colony, Great Blue Herons defend feeding territories from other herons with dramatic displays in which the birds approach intruders with their head thrown back, wings outstretched, and bill pointing skyward. Gulls and even humans may also be a target of this defensive maneuver.

Conservation

status via IUCN

Least Concern

Great Blue Heron numbers are stable and have been increasing in the U.S. since 1966, according to the North American Breeding Bird Survey. However, notable population declines have occured in some areas, particularly in the “great white heron” group in southern Florida, where elevated mercury levels in local waterways may be a factor. These herons can be found throughout the year all over North America, though most populations in Canada are present only during the breeding season, and most populations in Mexico are only present during the winter. Because Great Blue Herons depend on wetlands for feeding and on relatively undisturbed sites for breeding, they are vulnerable to habitat loss and to impacts such as traffic, logging, motorboats, and other human intrusions that can disrupt nesting colonies. Other threats include chemical pollutants or other causes of reduced water quality. Although contaminant levels have declined in many areas, pollutants such as PCBs and DDT and newer types of industrial chemicals continue to affect heron habitats and can contribute to factors such as reduced nest site attendance.

Credits

  • Vennesland, Ross G. and Robert W. Butler. 2011. Great Blue Heron (Ardea herodias). In The Birds of North America, No. 25 (A. Poole, Ed.). The Birds of North America Online, Ithaca, New York.
  • Butler, R. W. 1992. Great Blue Heron (Ardea herodias). In The Birds of North America, No. 25 (A. Poole, P. Stettenheim, and F. Gill, eds.). The Birds of North America Online, Ithaca, New York.
  • Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1988. The Birder’s Handbook. Simon & Schuster Inc., New York. Sibley, D. A. 2000. The Sibley Guide
  • Glahn, J. F., B. Dorr, J. B. Harrel, and L. Khoo. 2002. Foraging ecology and depredation management of great blue herons at Mississippi catfish farms. Journal of Wildlife Management 66: 194-201.
  • Seattle Audubon Society Great Blue Heron Fact Sheet.
  • Sibley, D. A. 2000. The Sibley Guide to Birds. Alfred A. Knopf, New York
  • USGS Patuxent Wildlife Research Center. 2011. Longevity Records of North American Birds.
  • USGS Patuxent Wildlife Research Center. 2012. North American Breeding Bird Survey 1966–2010 analysis.

Range Map Help

Great Blue Heron Range Map
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Migration

Partial migrant. Great Blue Herons generally move away from the northern edge of their breeding range in winter, with some flying as far south as the Caribbean. Populations in the Pacific Northwest and south Florida are present year-round.

Backyard Tips

Great Blue Herons aren’t likely to visit a typical backyard. However, they are sometimes unwelcome visitors to yards that include fish ponds. A length of drain pipe placed in the pond can provide fish with a place to hide from feeding herons. Herons, like most of our birds, are legally protected by the Migratory Bird Treaty Act.

Find This Bird

Scan shorelines, river banks, and the edges of marshes, estuaries, and ponds across much of the U.S. for this tall, slow-moving heron. Great Blue Herons also feed in meadows, farmland, and other open fields. Some colonies or “heronries” are found near developed areas; look for the herons’ bulky stick nests high in trees. And once you recognize their slow wingbeats and massive silhouettes, you’ll start to notice these birds in flight high in the sky as well.