The common moorhen (Gallinula chloropus), also known as the waterhen or swamp chicken, is a bird species in the rail family (Rallidae). It is distributed across many parts of the Old World.^{[2][circular reference]}

Quick Facts Conservation status, Scientific classification ...

Common moorhen
Adult G. c. chloropus and audio recording of call, both from France
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Gruiformes
Family:	Rallidae
Genus:	Gallinula
Species:	G. chloropus
Binomial name
Gallinula chloropus (Linnaeus, 1758)
Subspecies
About 5, see text
Range of G. chloropus   Breeding   Resident   Non-breeding   Probably extinct
Synonyms
Fulica chloropus Linnaeus, 1758 Fulica fusca Linnaeus, 1766

Close

The common moorhen lives around well-vegetated marshes, ponds, canals and other wetlands. The species is not found in the polar regions or many tropical rainforests. Elsewhere it is likely the most common rail species, except for the Eurasian coot in some regions.

The closely related common gallinule of the New World has been recognized as a separate species by most authorities,^{[2][circular reference]} starting with the American Ornithologists' Union and the International Ornithological Committee in 2011.^[3]

The name mor-hen has been recorded in English since the 13th century.^[4] The word moor here is an old sense meaning marsh;^[4] the species is not usually found in moorland. An older name, common waterhen, is more descriptive of the bird's habitat.

A "watercock" is not a male "waterhen" but the rail species Gallicrex cinerea, not closely related to the common moorhen. "Water rail" usually refers to Rallus aquaticus, again not closely related.

The scientific name Gallinula chloropus comes from the Latin Gallinula (a small hen or chicken) and the Greek chloropus (khloros χλωρός green or yellow, pous πούς foot).^[5]

The moorhen is a distinctive species, with predominantly black and brown plumage, with the exception of a white under-tail, white streaks on the flanks, yellow legs and a red frontal shield. The bill is red with a yellow tip. The young are browner and lack the red shield. The frontal shield of the adult has a rounded top and fairly parallel sides; the tailward margin of the red unfeathered area is a smooth waving line. In the related common gallinule (Gallinula galeata) of the Americas, the frontal shield has a fairly straight top and is less wide towards the bill, giving a marked indentation to the back margin of the red area.

The common moorhen gives a wide range of gargling calls and will emit loud hisses when threatened.^[6] A midsized to large rail, it can range from 30 to 38 cm (12 to 15 in) in length and span 50 to 62 cm (20 to 24 in) across the wings. The body mass of this species can range from 192 to 500 g (6.8 to 17.6 oz).^[7][8]

This is a common breeding and resident bird in marsh environments, rivers, well-vegetated lakes and even in city parks. Populations in areas where the waters freeze, such as eastern Europe, will migrate to more temperate climates. In China, common moorhen populations are largely resident south of the Yangtze River, whilst northern populations migrate in the winter, therefore these populations show high genetic diversity.^[9]

On a global scale – all subspecies taken together – the common moorhen is as abundant as its vernacular name implies. It is therefore considered a species of Least Concern by the IUCN.^[1] However, small populations may be prone to extinction. The population of Palau, belonging to the widespread subspecies G. c. orientalis and locally known as debar (a generic term also used for ducks and meaning roughly "waterfowl"), is very rare, and apparently the birds are hunted by locals. Most of the population on the archipelago occurs on Angaur and Peleliu, while the species is probably already gone from Koror. In the Lake Ngardok wetlands of Babeldaob, a few dozen still occur, but the total number of common moorhens on Palau is about in the same region as the Guam population: fewer than 100 adult birds (usually fewer than 50) have been encountered in any survey.^[11]

Other localised groups of common moorhen are starting to come under threat. The Royal Society for the Protection of Birds in the United Kingdom has the common moorhen classified as one of its 103 species whose conservation status is of moderate concern^[12] due to its recent population decine. The number of breeding pairs has fallen to its lowest level in the UK since 1966^[13] and has been protected under the Wildlife and Countryside Act (1981).

The common moorhen is one of the birds (the other is the Eurasian coot, Fulica atra) from which the cyclocoelid flatworm parasite Cyclocoelum mutabile was first described.^[14] The bird is also parasitised by the moorhen flea, Dasypsyllus gallinulae.^[15]

Five subspecies are today considered valid; several more have been described that are now considered junior synonyms. Most are not very readily recognizable, as differences are rather subtle and often clinal. Usually, the location of a sighting is the most reliable indication as to subspecies identification, but the migratory tendencies of this species make identifications based on location not completely reliable. In addition to the extant subspecies listed below, an undescribed form from the Early Pleistocene is recorded from Dursunlu in Turkey.^[16][17][18]

• collecting for nest, Wolvercote, Oxfordshire
• on nest, Wolvercote, Oxfordshire
• G. c. chloropus nest with small clutch of eggs at Wilgenhoek, Deerlijk (Belgium)
• Chick, 1–2 weeks old
• Moorhen feeding chick some regurgitated food.
• Immature G. c. chloropus, 3–4 months old, in Parc de Bercy, Paris (France)
• Juvenile, Strumpshaw Fen, Norfolk
• young adult, London