Courtesy Kenn Kaufman
A cosmopolitan species, the Great Egret is broadly distributed throughout tropical and temperate wetlands around the globe. In the Americas, it breeds from Canada to Argentina and Chile. Wintering populations can be found as far north as waters remain ice-free in North America. Generally this ranges from Oregon south along the West Coast, and along Mexico down to Panama, as well as throughout much of the southern United States, and up the Eastern Seaboard, sometimes into New York and Massachusetts during warmer years.
A legend for the range map to the right can be found here
Great Egrets inhabit all kinds of wetlands, both inland and along the coast, including marshes, river margins, lakeshores, coastal swamps, lagoons, mudflats, and manmade impoundments and drainage ditches. They can also be found in more terrestrial habitats, such as agricultural fields. Nesting takes place mostly in waterside trees or shrubs, often on islands.
Strictly carnivorous, Great Egrets stalk their prey by either standing still or walking slowly in shallow water and marshland. Their diet consists mainly of fish, but also includes aquatic invertebrates (particularly crustaceans), insects, amphibians, reptiles, other birds, and small mammals. Great Egrets feed individually or in loose flocks, sometimes with other herons, cormorants, and ibises. They sometimes forage in open fields.
At the beginning of the breeding season, Great Egrets develop long showy plumes, called aigrettes, which trail from their backs, and are prominently displayed during courtship. Their bills become orange-yellow and the skin around their eyes changes from yellow to lime-green. Seasonally monogamous, the birds typically nest in large colonies, often with other species such as Great Blue Herons or Snowy Egrets. A Great Egret pair produces a single brood each year, starting when the birds are two or three years of age. In temperate zones they breed in spring or summer, depending on when food is most abundant; in the tropics, they can breed at any time of the year. Their platform nests, made of twigs, are constructed in treetops or woody vegetation. Females lay one to six pale blue-green eggs, which both sexes incubate for about three weeks. Both parents care for the chicks, which can fly at six to seven weeks of age.
In North America, Great Egrets are migratory in their northern and interior breeding areas, but they are apparently influenced by temperature fluctuations. In milder winters, the birds may stay on their breeding grounds if the waters where they feed remain open. Spring migration occurs between late February and May, with birds occupying their summering grounds until late August through November, and sometimes even into December. They migrate individually or in small, V-shaped or wavy-lined flocks of less than 25, often following routes along coastlines and major rivers.