Green-backed herons rarely winter as far north as Pennsylvania. For years the birds had been killed for their long, white body plumes, used to feather women's hats. Strong conservation laws saved the species, which is repopulating its former range. A great egret's plumage is pure white, the bill yellow, and the legs and feet glossy black. Preferred foods are fish, small mammals, amphibians, and insects.
Egrets inhabit swamps, brushy lake borders, ponds, Susquehanna River shallows, islands and mudflats.
Nests are in colonies, sometimes with other heron species, usually 10-50 feet up in trees. Nests are made of sticks and twigs, two feet in diameter, sometimes lined with leaves, moss and grass. Incubation is performed by both sexes and takes 23-24 days. Breeding resident egrets arrive in April. Post-breeding dispersal occurs from July to October Migrants also pass through the state at this time.