Courtesy Kenn Kaufman
The Black-crowned Night-Heron breeds across most of the United States, except for the Appalachian Mountains into Maine, the upper Great Lakes, and the arid northern plains. The birds' breeding range extends into south central Canada and northeast along the St. Lawrence River. Most winter coastally on the Atlantic from New England through Florida, around the Gulf Coast, and on the Pacific from southern Oregon south. Black-crowned Night-Herons occur throughout most of South America outside the central Amazon watershed.
A legend for the range map to the right can be found here
Black-crowned Night-Herons are wetland habitat generalists, thriving on fresh and saltwater habitats alike. The birds use marshes, swamps, estuaries, lagoons, and mudflats, as well as altered wetlands, such as canals, flooded fields, human-made islands, and aquaculture sites, often foraging within vegetated cover. Small islands near marshes and wooded or brushy swamps provide breeding sites.
A still and patient predator, the Black-crowned Night-Heron has an omnivorous diet. This nocturnal forager uses vegetated wetlands to ambush small fish (carp, eel, minnows, shad, and shiners), crayfish, fiddler crabs, small snakes, mice, rats, chicks of other wading birds, insects (beetles, crickets, grasshoppers, and dragonflies), and even some plant matter. In shallow water, the Black-crowned Night-Heron may lure prey by vibrating its bill.
Black-crowned Night-Herons nest in colonies of mixed species. As early as December in Florida, males establish territories with bill snapping, twig shaking, and the construction of a loose platform. Males attract females with a "stretch display"—an exaggerated bow that accentuates the white plumed head. The male gathers twigs and passes them to the female, who constructs a shallow nest in a tree, shrub, or on the ground, and lines it with roots and grasses. For 24 to 26 days, both parents incubate three to five greenish eggs, then brood, feed, and defend the grayish hatchlings.
Black-crowned Night-Heron hatchlings feed on regurgitated food from the adults. Within ten days they can clamber out of the nest to avoid predators. After about three weeks, young birds exhibit defense mechanisms, include regurgitation. Depending on age differences, food availability, and brood size, siblings may attack each other. Black-crowned Night-Herons fledge in 6 to 7 weeks and may form small flocks near foraging areas, where they still beg for food from adults. Later they disperse outside the breeding area.
Black-crowned Night-Herons disperse after breeding, and this movement blends into fall migration which continues through October. Using routes along both coasts and the Mississippi River valley, most herons withdraw from the northern breeding range, but may be permanent residents south of the Carolinas.