Great Blue Heron
The Great Blue Heron is the largest North American heron. Great Blues have a varied diet, and they exploit a variety of habitats. Their range extends farther north than the ranges of most other herons. They are found throughout the United States and southern Canada, and along the Pacific Coast to southeastern Alaska. Fish are their primary prey, but they also eat insects, rodents, birds, and small reptiles and amphibians. They usually stalk and stab their prey in shallow water or on the ground. Great Blue Herons are often seen stalking meadow voles and shrews in fields. Sometimes they catch insects in flight, including grasshoppers, dragonflies, moths, and butterflies.
Great Blue Heron Range Map

Great Blue Herons nest in colonies that often include other species of herons. They usually build nests from 20 to 60 feet up in tall trees. Subtropical populations breed among mangroves, where nests may be placed on the ground on islands that lack predators. Along coastlines, Great Blue Herons may use cliff ledges and rock outcrops for nest sites. Males gather twigs and small branches that are up to a foot long and pass the material to the females who construct the nest. When first built, the nests are rather flimsy and shallow, but material is added each season as nests are reused, resulting in bulky nests up to 40 inches in diameter. They are lined with finer twigs, grass, and leaves. The female lays three to five light blue eggs. Clutch size tends to increase with latitude; Canadian populations have the largest average clutch sizes.

Nestlings in the rookeries are noisy. When the parents arrive with food, they make sounds that resemble the barking of puppies. For the first several weeks of the nestlings’ lives, at least one parent is present at all times. When threatened, young Great Blue Herons regurgitate over the edge of the nest onto their harassers. After two months they can fly, and by three months they leave the nest. After the breeding season, Great Blue Herons disperse, and some wander north of the breeding range. East of the Rockies, the northern populations migrate, with eastern birds moving south along the coast, and midwestern birds wintering along the Gulf Coast or in Texas or Mexico. Great Blue Herons tend to be permanent residents in the southeast, and along the West Coast as far north as southeastern Alaska.

Description: Great Blue Herons are easy to identify because of their distinctive coloration and large size—up to four feet tall, with a seven-foot wingspread. Herons fly with folded necks, distinguishing them from cranes, which fly with their necks extended. Great Blue Herons have blue-gray upperparts that are paler at the long neck. The crown of the head is white, with a dark streak over the eyes extending back as black plumes. The front of the neck is white with black streaking. The long and stout bill is yellow. The wings show dark primaries in flight. There is a black streak at the flanks, and at the front edge of the folded wing. The legs are grayish with rusty “pantaloons.”

Juvenile birds are gray all over, with dark crowns. The adult plumage is attained in the fall of the third year, but some immature characteristics may be retained such as dusky feathers in the white crown, or white feathers in the black shoulder tufts.

A distinct population of Great Blue Herons breeds on the mangrove islands off the Florida Coast. These Great White Herons are pure white, with greenish-yellow legs and yellow bill. Formerly, the Great White Heron was considered a separate species because of its color, slightly larger size, and restricted saltwater habitat; however it is now considered a color form of the Great Blue Heron. An intermediate type with the body coloration of a typical Great Blue Heron, but with an all-white head, is known as Wurdemann's Heron.



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