Courtesy Kenn Kaufman
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
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.
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.
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.
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.