Marianas Mallard

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Marianas Mallard

Anas oustaleti

ListedJune 2, 1977
FamilyAnatidae (Ducks and geese)
DescriptionMales have dark green heads with buff feathers; females are all brown with feathers edged with light brown.
HabitatWetlands, mangrove lagoons, streams and flooded fields.
FoodGreen vegetation and seeds in shallow water.
ReproductionClutch sizes range from 7-12.
ThreatsHabitat destruction, over-hunting.
RangeGuam, Marianas Islands


The Anas oustaleti (Marianas mallard) is 20-22 in (50.8-55.88 cm) in length with the silhouette of a mallard. The male (platyrhynchos type) has a dark green head with buff feathers intermingled along the sides. There is a dark brown streak running through the eye and a faint white ring on the lower neck. The sides of the body are vermiculated but some brown feathers are found even in the full nuptial plumage, with a lighter area under the wings. The upper breast is a dark reddish chestnut with dusky spots and the bill is black with an olive tip. The upper tail coverts are dark with white tail feathers, and the central upper tail coverts are dark and curled upward. The speculum is a dark blue, and the feet are a reddish orange color, darkening around the webs.

The male superciliosa-type has a dark brown head with brown and buffy on the sides of the head. The scapulars, sides of body and the upper breast are all dark brown with light brown margins. The tail is dark brown with no white, and the central upper tail coverts are flat. The speculum is usually dark blue or purple as in A. platyrhynchos but two specimens had dark green speculums. The bill is olive with black spot in center of mandible and the feet are dark orange, growing darker in the joints and webs.

Female platyrhynchos and superciliosa types are indistinguishable from each other and resemble A. superciliosa except for a blue speculum. They are all brown with feathers edged with light brown. The sides of face are marked with light yellow or buffy feathers, and a dark line runs through the eye with a buffy eye stripe above. The tail is brown and has flat feathers. The bill is either blackish or brownish.

A. oustaleti was first described in 1856 as a sub-species of A. boschas, based on one specimen from "Les Isles Malouines" in the Paris Museum. Thirty-eight years later the same specimen was examined and called A. oustaleti. The next six specimens were collected from Guam in 1888 and described by Oustalet. Since then the taxonomy of the species has been debated from time to time. The U.S. Fish and Wildlife Service considers Anas oustaleti a true species.


In a strict sense this species is nonmigratory. The Marianas mallard is known from only three small islands in the Mariana Archipelago (Guam, Tinian, Saipan). Inter-island movement of ducks between Saipan and Tinian, which are separated by 3 mi (4.8 km) of open ocean, does not occur. Movements probably occur as a means of obtaining food or in reaction to human disturbances. Inter-island movements between Guam and Rota (30-40 miles [48-64 km]) have been suspected but never proven.

Mating probably involves a strong pair bonding and ritualistic breeding behavior similar to common mallards, however, breeding behavior for this species has not been documented. Pair bonding occurs during the mating season, but the female is responsible for nest building and rearing of young. Young chicks stay with the female until fledging. The mallard breeds and nests from January to July, with more records occurring in June and July then at any other time. It is thought that mallards in the Marianas have only one clutch per year, which is laid in June or July, with an estimated incubation period of 28 days. Artificial propagation in captivity was not successful, so details are largely unavailable.

It can be assumed that parental care is similar to other species of dabbling ducks in the genus Anas, such as A. platyrhynchos. In this species the eggs are incubated and defended by the female. The young are precocial, following the female away from the nest shortly after hatching. Young birds remain in the female's care until they fledge. Unlike migratory species, where parental bonds are broken during the fall migration, related A. oustaleti have the potential of continued contact and genetic inbreeding in the small restricted wetland habitats in the island chain.

Very little information about the food habits of the Marianas mallard exists. A. oustaleti has been observed feeding on green vegetation and seeds in very shallow water. Assuming the diet of A. oustaleti is similar to A. platyrhynchos, they probably consume floating, emergent, and submerged non-woody plants, grasses, seeds, insects, crustaceans and snails.

Anas oustaleti tend to use dense cover in the middle of the hot tropical day.


The Marianas mallard typically inhabits wet-lands, particularly freshwater/brackish lakes and ponds adjacent to marshes, but mangrove lagoons, streams and flooded fields are also used. In 1984 wetlands in the Northern Marianas were rated as primary or secondary mallard habitat on the basis of water levels, nesting cover and size. Of the 12 surveyed wetlands only four ranked as having primary habitat potential.

Dense cover associated with inhabited wetlands includes large stands of rushes Scirpus juncoides, Phragmites karka, and various sedges. Also important for cover is the fern, Acrostichum aureum, which forms hammocks in several marshes. The largest complex of mallard habitat lies in southern Saipan, the Lake Susupe marsh area, a total of 150-200 acres (60-80 hectares) with peripheral marsh habitat. Other areas known to have been used by mallards are much smaller (e.g., breeding occurred on Lake Hagoi, a small pond of about 10 acres (4 hectares) surrounded by 40 acres (16 hectares) of marsh). Nests have been located in reed swamps and in streamside wetlands.


Recent surveys indicate that the Marianas mallard is extinct within the Northern Marianas Islands. Similar conclusions have already been reached for the Guam population. Without a viable population it is impossible to describe the current biology of the species. The recovery potential for the species faded when the captive breeding program failed.

The Marianas mallard was found on Guam in the Talofofo River Valley prior to the Second World War with few verified sightings after the war. Habitat destruction led to its probable extinction by the 1960s or early 1970s.

The Marianas mallard also occurred on the Northern Marianas Islands of Tinian and Saipan. This species has not been documented on any island north of Saipan.


The Marianas mallard has probably never been abundant in this small island chain where extensive wetland complexes do not occur. Based on historical information the primary reasons for the decline of the Marianas mallard are habitat destruction, over-hunting and inadequate regulatory mechanisms in the past.

Prior to the Second World War, vast areas of Saipan and Tinian were cleared and wetlands were filled for agricultural purposes. Little native vegetation remained. The Second World War also had a devastating impact on mallard habitat. Saipan in particular was virtually leveled by bombs and artillery in 1944. Since the war the two islands that supported mallards, Saipan and Guam, have experienced large scale land development projects such as airports, housing developments, tourist facilities, military bases, and modern roads. Some of these projects have reduced the amount and quality of the habitat. New roads that cross the Chalan Kanoa Marsh near Lake Susupe (major mallard habitat) have altered the natural drainage of the wetland, increasing its salinity and affecting plant succession.

Excessive hunting and collecting during the prewar and post-war eras contributed to the decline of the Marianas mallard. During their pre-war occupation the Japanese collected 30-40 specimens which reduced an already small gene pool just prior to and during the peak of habitat destruction. During and immediately after island fighting in the Second World War, people were forced to live off the land, including wildlife for sustenance. There is a distinct possibility that several mallards were killed during this period.

Wild ducks were killed illegally by hunters on Saipan and Tinian as late as the 1970s. Both migratory and the native species were subject to mortality from hunters when the Marianas mallard population was very small. There was and still is a definite lack of enforcement of game laws at the local level, even though the duck has been protected by Territorial and Federal laws since the early 1970s.

Based on recent surveys in the Mariana Islands, the Marianas mallard is probably extinct. As a result of these findings a discussion of future threats is academic. However, the existing wetlands that support other wildlife species (including the endangered race of common moorhen, Gallinula chloropus guami ) will continue to suffer in the future from development projects similar to those mentioned above.

Conservation and Recovery

The Marianas mallard is jeopardized by its limited area of habitat and small population. It appears to have succumbed to over-hunting. Hope for its rediscovery steadily diminishes with the repeated but unsuccessful surveys by local and Federal wildlife biologists, many of whom now consider the bird extinct. Although a recovery plan has been drafted, it seems likely that, upon impending completion of a status report, the species will be considered for de-listing, owing to extinction. In the meantime, the following recovery actions have been recommended: (1) Continued surveys to locate the mallard, (2) Continued prohibition of hunting, (3) Rigorous protection of all wetlands in the Marianas (this would include the following: acquisition of wetlands [especially Hagoi area on Tinian, and Lake Susupe and its surrounding wet-land areas on Saipan], control and restrict pollution, restrict development, restrict boating activities that harass the birds, maintain water tables, maintain/control water flows, maintain/control water salinity levels, and develop a wetland management plan that favors wetland species, particularly on Saipan and Tinian where the mallard was last seen), (4) Preventing the introduction of feral mallards and other domestic waterfowl to wet-lands of Marianas, and (5) If any birds should be found, captive breeding is considered essential.

Recovery actions underway include ongoing surveys and law enforcement by the Commonwealth of Northern Marianas Islands Division of Fish and Wildlife and review of development projects affecting wetlands.


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


U. S. Fish and Wildlife Service "Mariana Mallard /Anas platyrhynchos oustaleti. Threatened and Endangered Species.

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Marianas Mallard

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