Black-crowned Night Heron

Common name: Black-crowned night-heron
Class: Aves
Order: Ciconiformes
Family: Ardeidae
Genus: Nycticorax
Species: Nycticorax nycticorax
 

photo M. Noonan


Taxonomy/ description

The Black-crowned Night Heron has a stocky body, with a short neck and legs. Adult night heronís 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 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 juvenile also has a brown head, neck, chest and belly streaked with white. The wings and back are darker brown, though the tips of the feathers have large white spots.

Habitat/ diet

The black-crowned night heron is found across North America from Washington through Quebec, south through coastal Mexico, as well as locally in Central America and the Caribbean. Some winter as far north as Oregon and the New England states.

Most colonies of black-crowned night herons are associated with large wetlands. They inhabit a variety of wetland 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 heronís diet consists mainly of fish, though it also eats as leeches, earthworms, and insects. It also eats crayfish, mussels, squid, amphibians, lizards, snakes, rodents, birds, eggs, carrion, plant materials, and garbage and refuse at landfills.

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.
 

photo M. Noonan


Behavior/ reproduction

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. It is also a migrating species. 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. The eggs are laid at 2 day intervals, beginning 4-5 days after pair formation. Incubation, which lasts 24-26 days, is carried out by both adults. After 2 weeks, the young leave the nest. By 3 weeks, they can be found clustered at the tops of trees if they are disturbed. By Week 6-7 they fly well and depart for the feeding grounds. 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.

Where to see them in WNY

One good place to find the Black-crowned night-heron is on the Swallow Hollow Trail at the Iroquois National Wildlife Refuge. From the parking lot, take the trail heading to the left. Be sure to begin looking once you reach the earthen dike; emergent marshes like this one are great habitats for these birds.

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