Mariana Common Moorhen

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Mariana Common Moorhen

Gallinula chloropus guami

ListedAugust 27, 1984
DescriptionAn aquatic, fowl-like bird.
HabitatFreshwater tropical wetlands.
FoodAquatic plants and invertebrates.
ReproductionLays eggs in a ground nest; both parents care for the young.
ThreatsHabitat loss, excessive hunting, predation by introduced animals, competition with introduced fish.
RangeGuam, Tinian, Saipan, Pagan in the Mariana Islands


The Mariana common moorhen, also known as the Mariana common gallinule, is an overall dark-colored bird. It has: sooty black on the head and neck; dark-bluish slate-gray on the upper back; brownish on the lower back and wing-coverts; blackish-brown on the tail; dark brown on the wings; white on the outer edge of the first wing primary; dark slate-gray on the breast and upper abdomen; dark underwings with white edges; white under-tail coverts; a red bill and frontal shield; yellowish on the tip of the bill; and olive-green legs and feet. The adult female resembles the adult male, but has a smaller frontal shield on the base of the top of the beak. Immature birds resemble the adults, but the plumage is more mottled with white and brown, and the frontal shield is small.


The Mariana common moorhen is a non-migratory, wary bird that seeks cover in nearby vegetation if disturbed by humans. It feeds on aquatic plants and invertebrates, which are obtained by swimming and sticking the head under the surface to grasp plants or insect prey. It also forages while walking along shorelines. The nest is a raised mound of vegetation beside a wetland. The clutch size is between four and eight eggs, and it may breed several times in a year.


The Mariana common moorhen inhabits tropical freshwater lakes, marshes swamps, and wet rice paddies. It prefers open water fringed by emergent aquatic plants.


The Mariana common moorhen is a local (or endemic) species that occurs only on the islands of Guam, Pagan, Saipan, and Tinian, in the Marianas group of the western Pacific Ocean.


The decline of the Mariana common moorhen is partly due to excessive hunting, as this species is highly prized by local Chamorros people as food. It has also suffered the loss of most of its wetland habitat. The introduced brown tree snake (Boiga irregularis ), a known avian predator, may also be affecting the moorhen on Guam. Free-running dogs may also be killing this rare bird. A recent estimate of the Guam population was less then 100 individuals; numbers on the other islands are not known.

Conservation and Recovery

Enhancement of the Mariana common moorhen requires the conservation and management of its essential wetland habitat. Initial activities should focus on the permanent waterbodies that provide refuge habitat during the dry season. Temporary ponds and marshes that fill during the monsoonal rains are also important. Other closely related species of moorhens are well known to respond favorably to habitat improvement. Management activities that would enhance the Mariana common moorhen include controlling water levels in wetlands, creating islands for safer nesting, prescribed dredging to develop larger areas of open water and edge habitat, controlling noxious weeds and introduced predators, and controlling alien fish that may be competing with moorhens for food. Ecological research is needed in support of these management practices. The U. S. Fish and Wildlife Services believes that management could allow the population of Mariana common moorhens to be increased to at least several hundred birds on Guam, 150 on Tinian, and 150 on Saipan.


U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
(503) 231-6121

U. S. Fish and Wildlife Service, Ecological Services
300 Ala Moana Blvd, Room 3-122
P. O. Box 50088
Honolulu, Hawaii 96850
Telephone: (808) 541-3441
Fax: (808) 541-3470


Conservation Management Institute. 14 March 1996."Mariana common moorhen." Virginia Tech, Endangered Species Information System. ( Date Accessed: July 6, 2000.

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Mariana Common Moorhen

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