TAXONOMY

Black-crowned Night-Herons are Ardeids which means they are in the family consisting of other herons. The Black-crowned Night-Heron has a stocky body, with a short neck and legs. Adult night-heron’s have a distinctive coloring, with a black cap and upper back, gray wings, rump and tail, and a white to pale gray underbelly. Its bill is stout and black, and its eyes are red. For most of the year, the legs of an adult night-heron are yellow-green, but by the height of the breeding season, they turn pink. The juvenile has a brown head and body streaked with white. The eyes of the juvenile black-crowned night heron are yellowish or amber, and the dull gray legs lack the colorful pigmentation of those of the adult. The wings and back are darker brown and the tips of the feathers have large white spots.

The Black-crowned Night-Heron is found across North America from Washington through Maine, south through coastal Mexico, as well as locally in Central America and the Caribbean. The Black-crowned Night-Heron mainly winters on the coast and in Mexico.

Most colonies of Black-crowned Night-Herons are associated with large wetlands. They inhabit a variety of wetland and riparian habitats such as swamps, streams, rivers, marshes, mud flats and the edges of lakes that have become overgrown with rushes and cattails. The Black-crowned Night-Heron's diet consists mainly of fish, though it also eats as leeches, earthworms, and insects. It also eats a variety of other aquatic animals including  crayfish, clams, amphibians, snakes, rodents, birds, eggs, carrion, and garbage and refuse at landfills.

BEHAVIOR

Black-crowned Night-Herons are usually solitary foragers, and strongly defend their feeding territory. The night heron prefers to feed in shallow waters, where it grasps its prey with its bill instead of stabbing it. A technique called 'bill vibrating,' which is opening and closing the bill rapidly in water, creates a disturbance which may lure prey. Evening to early morning are the usual times it feeds, but when food is in high demand, such as during the breeding season, it will feed at any time of the day.

Black-crowned Night-Herons are social at all times of the year, associating with other species of herons frequently. In the winter, it roosts communally. The fact that this night-heron feeds throughout the night means that it avoids competition with day herons which use the same habitat. Feeding sites are used repeatedly. Black-crowned Night-Herons defend both feeding and nesting territory. Also, their young can be aggressive, regurgitating or defecating on human intruders.

Black-crowned Night-Herons are thought to be monogamous. Pair formations are signaled by males becoming aggressive and performing snap displays, in which they walk around in a crouched position, head lowered, snapping their bills together or grasping a twig. The snap display is then followed by the advertisement display, sometimes called the stretch, snap-hiss, or song-and-dance display, to attract females. In this display a male stretches his neck out and bobs his head, and when his head is level with his feet, he gives a snap-hiss vocalization. Females that come near the displaying male are rejected at first, but eventually a female is allowed to enter his territory. Mating usually takes place on or near the nest, and begins the first or second day after the pair is formed. There is one brood per season. Black-crowned Night-Herons nest colonially, and often there can be more than a dozen nests in one tree. The nest is built near the trunk of a tree or in the fork of branches. Incubation, which lasts 24-26 days, is carried out by both adults. After 2 weeks, the young leave the nest. Adult Black-crowned Night-Herons do not recognize their own young and will accept and brood young from other nests. The young have a tendency to regurgitate their food onto intruders when disturbed.