Perception Channels: visual ; tactile ; acoustic ; chemical
The night heron has a stocky body, with a comparatively short neck and legs. The length averages 58-72 cm, with the females averaging slightly smaller than the males. The adult has distinctive coloring, with black cap, upper back and scapulars; gray wings, rump and tail; and white to pale gray underparts. The bill is stout and black, and the eyes are red. For most of the year, the legs of the adult are yellow-green, but by the height of the breeding season, they have turned 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 has a brown head, neck, chest and belly streaked with buff and white. The wings and back are darker brown, though the tips of the feathers have large white spots. These spots are particularly large on the greater secondary coverts. The young do not acquire full adult plumage until the third year. (Davis, 1993; http://www.mbr.nbs.gov/id/htmid/h2020id.html)
Other Physical Features: endothermic ; bilateral symmetry
Average mass: 800 g.
Average lifespan
Status: wild: 253 months.
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. (Davis, 1993; http://www.biology.ualberta.ca/uamz.hp/heron.html)
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. The Old World race 'nycticorax' occurs from Europe to Japan, Africa and India. (Davis, 1993)
Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native )
The black-crowned night heron is an opportunistic feeder. Its diet consists mainly of fish, though it is frequently rounded out by other items such as leeches, earthworms, aquatic and terrestrial insects. It also eats crayfish, mussels, squid, amphibians, lizards, snakes, rodents, birds, eggs, carrion, plant materials, and garbage and refuse at landfills. It is usually a solitary forager, and it strongly defends its 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. (Davis, 1993)
Black-crowned night herons have been hunted for food, though they are hunted for this purpose much less frequently now.
At fish hatcheries, humans claimed that the amount of fish the birds were consuming were becoming destructive. If they nest near human settlements, they are considered pests. (Davis, 1993)
In the late 1960s, declines in many black-crowned night heron populations were noted, and were attributed to the use of DDT. The status of these populations is indicative of environmental quality due to the high rank of these birds in the food chain, and their wide geographic distribution.
Adults were often killed or trapped near fish-culture establishments, due to their fishy diet, but other methods of discouraging them from eating the fish are now available. It is estimated that 1,300 birds were killed per year at fish hatcheries in nine states. Herons that nested too close to human settlements were considered pests and were also often killed, but other methods that do not involve killing have been developed. Since most populations are stablized or increasing, management has not been a major focus, though habitat destruction is an important factor in the conservation of this species. (Davis, 1993) This is a species of special concern in Michigan.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: special concern
IUCN Red List of Threatened Species: least concern
Black-crowned night herons are presumed 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 mandibles together or grasping a twig. The Snap Display is 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. Twig-shaking and preening may be occur between songs. It has been suggested that these displays provide social stimulus to other birds, prompting them to display. This stimultion in colonial species may be crucial for successful reproduction. Females that come near the displaying male are rejected at first, but eventually a female is allowed to enter his territory. The newly-formed pair then allopreens and engages in mutual billing. At the time of pair formation, the legs of both sexes turn pink. Copulation 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, either in the open or deep in foliage. The male initiates nest building by beginning to build a new nest or refurbishing an old one. The nest is usually a platform lined with roots and grass. During and after pair formation, the male collects sticks and presents them to the female, who works them into the nest. The male's twig ceremony gradually changes to nest building.
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. The clutch size is 3-5 eggs. The eggs are greenest on the first day and fade to pale blue or green after that. On hot days, the parents wet their feathers, perhaps to keep the eggs cool. Both parents brood the young. After 2 weeks, the young leave the nest, although they don't go far. 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 tendancy to regurgitate their food onto intruders when disturbed. (Davis, 1993)
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Average time to hatching: 25 days.
Average eggs per season: 4.
Average age at sexual or reproductive maturity (male)
Sex: male: 730 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 730 days.
Resident breeder?, regular passage visitor and winter visitor.
A small (23-28 inches), thick-set heron, the Black-crowned Night-Heron is most easily identified by its gray wings, black back and head, pale breast, and, in the breeding season, twin white head plumes. Where their ranges overlap, this species may be distinguished from its relative, the Yellow-crowned Night Heron (Nyctanassa violacea), by the latter species’ black face, gray breast, and, logically, by its yellow crown. Male and female Black-crowned Night-Herons are similar in all seasons. The Black-crowned Night Heron inhabits every continent except Australia and Antarctica. In the North America, this species breeds at lower elevations across much of the United States and southern Canada. Some populations in warmer areas are non-migratory, but others migrate south to the southern U.S., interior Mexico, and Central America. Elsewhere in the New World, other populations exist in the West Indies, coastal Mexico, southern Central America, and South America south to southern Argentina and Chile. In the Old World, this species inhabits warmer parts of Europe, Asia, and Africa, with populations ranging from sedentary to fully migratory depending on climate and habitat. Black-crowned Night-Herons inhabit a variety of wetland habitats, whether flowing or standing, large or small, and freshwater or saltwater. In tropical areas, this species may be found in mangrove wetlands and lagoons. Black-crowned Night Herons primarily eat a number of plant and animal foods, including small fish, crustaceans, mollusks, reptiles, small mammals, and aquatic plant seeds and vegetation. Black-crowned Night-Herons may be best observed wading in shallow water, where they may be seen plunging their bills into the water to catch fish. It is also possible to see Black-crowned Night Herons at their nesting colonies, especially when they return to roost, or while flying with their feet extended and their necks pulled in. As its name suggests, this species hunts mainly from sunset to sunrise, although individuals may be seen during the morning and afternoon as well.
A small (23-28 inches), thick-set heron, the Black-crowned Night-Heron is most easily identified by its gray wings, black back and head, pale breast, and, in the breeding season, twin white head plumes. Where their ranges overlap, this species may be distinguished from its relative, the Yellow-crowned Night Heron (Nyctanassa violacea), by the latter species’ black face, gray breast, and, logically, by its yellow crown. Male and female Black-crowned Night-Herons are similar in all seasons. The Black-crowned Night Heron inhabits every continent except Australia and Antarctica. In the North America, this species breeds at lower elevations across much of the United States and southern Canada. Some populations in warmer areas are non-migratory, but others migrate south to the southern U.S., interior Mexico, and Central America. Elsewhere in the New World, other populations exist in the West Indies, coastal Mexico, southern Central America, and South America south to southern Argentina and Chile. In the Old World, this species inhabits warmer parts of Europe, Asia, and Africa, with populations ranging from sedentary to fully migratory depending on climate and habitat. Black-crowned Night-Herons inhabit a variety of wetland habitats, whether flowing or standing, large or small, and freshwater or saltwater. In tropical areas, this species may be found in mangrove wetlands and lagoons. Black-crowned Night Herons primarily eat a number of plant and animal foods, including small fish, crustaceans, mollusks, reptiles, small mammals, and aquatic plant seeds and vegetation. Black-crowned Night-Herons may be best observed wading in shallow water, where they may be seen plunging their bills into the water to catch fish. It is also possible to see Black-crowned Night Herons at their nesting colonies, especially when they return to roost, or while flying with their feet extended and their necks pulled in. As its name suggests, this species hunts mainly from sunset to sunrise, although individuals may be seen during the morning and afternoon as well.
The black-crowned night heron (Nycticorax nycticorax), or black-capped night heron, commonly shortened to just night heron in Eurasia, is a medium-sized heron found throughout a large part of the world, including parts of Europe, Asia, and North and South America. In Australasia it is replaced by the closely related nankeen night heron (N. caledonicus), with which it has hybridized in the area of contact.
The black-crowned night heron was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae. He placed it with herons, cranes and egrets in the genus Ardea and coined the binomial name Ardea nicticorax.[2] It is now placed in the genus Nycticorax that was introduced in 1817 by the English naturalist Thomas Forster for this species.[3][4] The epithet nycticorax is from Ancient Greek and combines nux, nuktos meaning "night" and korax meaning "raven". The word was used by authors such as Aristotle and Hesychius of Miletus for a "bird of ill omen", perhaps an owl. The word was used by the Swiss naturalist Conrad Gessner in 1555 and then by subsequent authors for a black-crowned night heron.[5][6]
Four subspecies are recognised:[4]
In the Falkland Islands, the bird is called quark, which is an onomatopoeia similar to its name in many other languages, like qua-bird in English, kwak in Dutch and West Frisian, kvakoš noční in Czech, квак in Ukrainian, кваква in Russian, vạc in Vietnamese, kowak-malam in Indonesian, and waqwa in Quechua.
Adults have a black crown and back with the remainder of the body white or grey, red eyes, and short yellow legs. They have pale grey wings and white under parts. Two or three long white plumes, erected in greeting and courtship displays, extend from the back of the head. The sexes are similar in appearance although the males are slightly larger. Black-crowned night herons do not fit the typical body form of the heron family. They are relatively stocky with shorter bills, legs, and necks than their more familiar cousins, the egrets and "day" herons. Their resting posture is normally somewhat hunched but when hunting they extend their necks and look more like other wading birds.
Immature birds have dull grey-brown plumage on their heads, wings, and backs, with numerous pale spots. Their underparts are paler and streaked with brown. The young birds have orange eyes and duller yellowish-green legs. They are very noisy birds in their nesting colonies, with calls that are commonly transcribed as quok or woc.
Measurements:[7]
The breeding habitat is fresh and salt-water wetlands throughout much of the world. The subspecies N. n. hoactli breeds in North and South America from Canada as far south as northern Argentina and Chile, N. n. obscurus in southernmost South America, N. n. falklandicus in the Falkland Islands, and the nominate race N. n. nycticorax in Europe, Asia and Africa. Black-crowned night herons nest in colonies on platforms of sticks in a group of trees, or on the ground in protected locations such as islands or reedbeds. Three to eight eggs are laid.
This heron is migratory in the northernmost part of its range, but otherwise resident (even in the cold Patagonia). The North American population winters in Mexico, the southern United States, Central America, and the West Indies, and the Old World birds winter in tropical Africa and southern Asia.
A colony of the herons has regularly summered at the National Zoo in Washington, D.C. for more than a century.[8] The birds also prominently live year-round in the shores around the San Francisco Bay, with the largest rookery in Oakland.[9] Their ever presence at Oakland's Lake Merritt and throughout the city's downtown area, as well as their resilience to the urban environment and displacement efforts, have led to them being named Oakland's official city bird.[9]
There are two archaeological specimens of the black-crowned night heron in Great Britain. The oldest is from the Roman London Wall and the more recent from the Royal Navy's late medieval victualling yards in Greenwich.[10] It appears in the London poulterers' price lists as the Brewe, a bird which was thought to have been the Eurasian whimbrel or glossy ibis, which has now been shown to refer to the black-crowned night heron, derived from the medieval French Bihoreau.[11] Black-crowned night heron may have bred in the far wetter and wider landscape of pre-modern Britain. They were certainly imported for the table so the bone specimens themselves do not prove they were part of the British avifauna. In modern times the black-crowned night heron is a vagrant and feral breeding colonies were established at Edinburgh Zoo from 1950 into the 21st century[12] and at Great Witchingham in Norfolk, where there were 8 pairs in 2003 but breeding was not repeated in 2004 or 2005.[13] A pair of adults were seen with two recently fledged juveniles in Somerset in 2017, which is the first proven breeding record of wild black-crowned night herons in Great Britain.[14]
These birds stand still at the water's edge and wait to ambush prey, mainly at night or early morning. They primarily eat small fish, leeches, earthworms, mussels, squid,[15] crustaceans (such as crayfish),[16] frogs, other amphibians,[17] aquatic insects, terrestrial insects, lizards, snakes,[18] small mammals (such as rodents),[19] small birds, eggs, carrion, plant material, and garbage and refuse at landfills.[20] They are among the seven heron species observed to engage in bait fishing; luring or distracting fish by tossing edible or inedible buoyant objects into water within their striking range – a rare example of tool use among birds.[21][22] During the day they rest in trees or bushes. N. n. hoactli is more gregarious outside the breeding season than the nominate race.
A thorough study performed by J. Sitko and P. Heneberg in the Czech Republic in 1962–2013 suggested that the central European black-crowned night herons host 8 helminth species. The dominant species consisted of Neogryporhynchus cheilancristrotus (62% prevalence), Contracaecum microcephalum (55% prevalence) and Opistorchis longissimus (10% prevalence). The mean number of helminth species recorded per host individual reached 1.41. In Ukraine, other helminth species are often found in black-crowned night herons too, namely Echinochasmus beleocephalus, Echinochasmus ruficapensis, Clinostomum complanatum and Posthodiplostomum cuticola.[23]
Egg
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N. n. hoactli, Tobago
Feeding
Wading, Arches National Park, Utah
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juvenile in flight, Cyprus
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adult in flight, Cyprus
Eating a Goldfish, Toronto
A night heron building a nest. The black-crowned night heron (Nycticorax nycticorax), or black-capped night heron, commonly shortened to just night heron in Eurasia, is a medium-sized heron found throughout a large part of the world, including parts of Europe, Asia, and North and South America. In Australasia it is replaced by the closely related nankeen night heron (N. caledonicus), with which it has hybridized in the area of contact.
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