Black-crowned Night Heron

About the black-crowned night heron

The black-crowned night heron, sometimes called the black-capped night heron or simply the night heron in Eurasia, is a medium-sized heron with one of the widest distributions of any heron species, found across large parts of Africa, Asia, Europe, and North and South America. In Australasia, its ecological role is filled by the closely related Nankeen night heron, with which it has been known to hybridize where their ranges meet. Four subspecies are recognized, spanning from Eurasia and Africa to the Americas and the Falkland Islands, and differing only slightly from one another in plumage tone.

Adults have a black crown and back set against a body that is otherwise white or grey, with red eyes and short yellow legs. The wings are pale grey and the underparts white. One to eight slender white plumes — usually two to four — extend from the back of the head and are raised during greeting and courtship displays. Males and females look similar, though males run slightly larger. Compared to familiar day herons and egrets, the black-crowned night heron doesn't fit the typical heron mold: it's noticeably stockier, with a shorter bill, shorter legs, and a shorter neck. At rest it holds a hunched posture, but when hunting it extends its neck and looks much more like its wading relatives. During courtship at the start of the nesting season, an adult's legs briefly turn bright salmon-pink and the bare skin around its eyes turns blue.

Immature birds look quite different from adults: dull grey-brown on the head, wings, and back, marked with pale "teardrop" spots, and paler, brown-streaked underparts. Their eyes are orange rather than red, and their legs a duller yellowish-green. It takes until the second or third year for young birds to take on adult-like plumage, though they still lack the head plumes until fully mature.

The species was formally described by the Swedish naturalist Carl Linnaeus in 1758, who placed it with herons, cranes, and egrets under the name Ardea nycticorax. It was moved to its own genus, Nycticorax, by the English naturalist Thomas Forster in 1817. That name comes from Ancient Greek words for "night" and "raven," a pairing once used for any "bird of ill omen." The bird carries onomatopoeic names in many languages that echo its call, including quark in the Falkland Islands, kwak in Dutch, and vạc in Vietnamese.

Behavior and diet

Black-crowned night herons hunt by standing still at the water's edge and ambushing prey, mainly at night, early morning, or evening — behavior reflected in both their common name and their scientific one, which combines Greek words for "night" and "raven." Their diet is broad and opportunistic: small fish, leeches, earthworms, mussels, squid, crustaceans such as crayfish, frogs and other amphibians, aquatic and terrestrial insects, lizards, snakes, small mammals like rodents, small birds, eggs, carrion, plant material, and even garbage at landfills. They rest during the day in dense trees or bushes rather than being active in daylight.

Notably, the species is among just seven heron species documented engaging in bait fishing — tossing edible or inedible floating objects into the water to lure or distract fish within striking range, a rare example of tool use in birds. The American subspecies, N. n. hoactli, tends to be more gregarious outside the breeding season than the nominate Eurasian form.

Black-crowned night herons breed in colonies, nesting on platforms of sticks built in groups of trees, or on the ground in protected spots such as islands or reedbeds. A typical clutch runs three to eight eggs. They are noisy in their nesting colonies, with calls commonly transcribed as "quok" or "woc."

Range and habitat

The black-crowned night heron breeds in fresh and salt-water wetlands across much of the world. The nominate subspecies breeds through Europe, Asia, and Africa; a second subspecies ranges from Canada south through the United States and Central America to northern Argentina and Chile, plus Hawaii; a third occupies the southernmost tip of South America; and a fourth is confined to the Falkland Islands.

The species is migratory in the northern parts of its range but resident elsewhere, even through the cold of Patagonia. European birds winter in Africa, with a few remaining in southern Spain; central and east Asian birds winter in southern Asia; and North American birds winter in Mexico, the southern United States, Central America, and the West Indies. In the U.S., a colony has summered at the National Zoo in Washington, D.C., for more than a century, and the birds live year-round around San Francisco Bay, with the largest rookery in Oakland — a presence so established that the species has been named Oakland's official city bird.

Conservation status

The black-crowned night heron is listed as Least Concern (LC) by the IUCN, reflecting its broad global range. Its adaptability to both natural wetlands and urban environments is evident in its long-running colonies in Washington, D.C., and the San Francisco Bay Area. In Great Britain, where the species is now only a vagrant rather than a breeding resident, archaeological bone specimens from the Roman London Wall and medieval Greenwich show it was once part of the region's historical record, and a pair with fledged young in Somerset in 2017 marked the first confirmed wild breeding record there in modern times.