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 hybridised in the area of contact.

Taxonomy and name

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 nycticorax, based on specimens from southern Europe. It is now placed in the genus Nycticorax that was described in 1817 by the English naturalist Thomas Forster for this species. The epithet nycticorax is from Ancient Greek and combines , meaning "night" and 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.

Four subspecies are accepted:

thumb|Adult black-crowned night heron of subspecies N. n. obscurus showing grey plumage.The subspecies differ little; nominate N. n. nycticorax and N. n. hoactli are particularly similar in plumage (some authors have considered N. n. hoactli a synonym of the nominate

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Distribution

The breeding habitat is fresh and salt-water wetlands throughout much of the world. The nominate subspecies N. n. nycticorax breeds in Europe, Asia and Africa, subspecies N. n. hoactli in North and South America from Canada as far south as northern Argentina and Chile, N. n. obscurus in southernmost South America, and N. n. falklandicus in the Falkland Islands. 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 northern parts of its range, but is otherwise resident (even in the cold Patagonia). European birds winter in Africa (with a few staying in southern Spain), central and east Asian birds winter in southern Asia, and North American birds winters in Mexico, the southern United States, Central America, and the West Indies.

A colony of the herons has regularly summered at the National Zoo in Washington, D.C., for more than a century. The birds also prominently live year-round in the shores around the San Francisco Bay, with the largest rookery in Oakland. 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. 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. 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 (excluding the feral breeding colonies that were established at Edinburgh Zoo from 1950 into the start of the 21st century and at Great Witchingham in Norfolk, where there were eight pairs in 2003 but breeding was not repeated subsequently). 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.

Behaviour

thumb|upright=0.8| Juvenile in an "upright" threat display

These birds stand still at the water's edge and wait to ambush prey, mainly at night, early morning or evening. They primarily eat small fish, leeches, earthworms, mussels, squid, crustaceans (such as crayfish), During the day they rest in dense trees or bushes. N. n. hoactli is more gregarious outside the breeding season than the nominate race.

Parasites

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 eight 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, including Echinochasmus beleocephalus, Echinochasmus ruficapensis, Clinostomum complanatum and Posthodiplostomum cuticola.

  • Black-crowned Night Heron Species Account – Cornell Lab of Ornithology
  • Black-crowned night-heron - Nycticorax nycticorax - USGS Patuxent Bird Identification InfoCenter