The black-crowned night heron was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae.

[5][6] Four subspecies are accepted:[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, hoactli ("wactli") in Nahuatl (cf.

Adults have a black crown and back with the remainder of the body white or grey, red eyes, and short yellow legs.

For a short period during courtship at the start of the nesting season, the legs of adults turn bright salmon-pink, and the bare skin around the eyes blue.

[8] Immature birds have dull grey-brown plumage on their heads, wings, and backs, with numerous pale "teardrop" spots.

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.

The oldest is from the Roman London Wall and the more recent from the Royal Navy's late medieval victualling yards in Greenwich.

[12] 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.

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.

[citation needed] 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.