Micronesian Megapode

Megapodius laperouse

Description

Micronesian megapode, Megapodius laperouse, is a small, stout, robust chicken-like bird standing 6.9-7.8 in (17.5-20 cm) tall. Sexes are similar in color and plumage, with the males being slightly larger. Their general color is dark grayish brown to brownish black with an ash grey or silver crest pointing backward from the top of the head. The head is thinly feathered dark grey with dark reddish bare skin at the gape of the beak and also in a well-developed gular patch. The chicken-like beak is a bright yellow with large nostril and a black line running down the top of the maxilla. The crest has short, silvery, pointed feathers directed upward and backward to form a pointed top notch. The wings are short (7.3 in; 18.5 cm), broad and rounded similar in size and shape to ruffed-grouse wings and a uniform grayish brown. Micronesian megapode's tail is short (2-2.2 in; 5-5.5 cm) and slightly pointed, with dark grayish brown above and brown to reddish brown on the undertail coverts. The legs and feet are large, well-developed, and a bright yellow or orange.

There are two subspecies recognized: M. laperouse laperouse, 1823, from the Mariana Islands and M. laperouse senex, 1867, from the Palau Islands. The Palau subspecies is distinguished by a lighter pearl grey crest and top of head that shows a more marked contrast with the body than in M. laperouse laperouse. In close examination M. laperouse laperouse has more olivaceous brown in the wing coverts and scapulars and the underparts are generally more pale than in M. laperouse senex. The Mariana sub-species has a dark ash gray crest and top of head. The species was first described from the Marianas in 1823 as Megapodius La Perouse. The Mariana sub-species has since undergone a variety of minor name changes, variations of the species name La Perouse. The subspecies laperousei was assigned in 1922. The subspecies in the Palaus was described in 1967 as M. senex. It was combined with the Mariana species in 1893. Common names for this species include: Marianas megapode, Micronesian megapode, incubator bird, Micronesian incubator bird. By far the most common and up to date citations refer to the species as the Micronesian megapode, including the bird list from the Association of Systematic Collections (ASC). The Federal Register common name was changed to Micronesian megapode. It is more meaningful and geographically descriptive than the previous name, LaPerouse's megapode, and conforms to the ASC list. "Sasangat" is the vernacular name for M. laperouse in the Chamorro language of the Mariana Islands. "Bekai" is the local name in Palau. The species is also commonly known as scrubfowl.

Behavior

Micronesian megapode is a rather communal species and is found in relatively high densities under the right conditions. Apparently nesting areas are not actively defended since more than one pair will congregate at historical nesting grounds where eggs are laid in a communal nest mound. Birds commonly forage individually, in pairs, or in small groups. Micronesian megapode is non-migratory in the sense of long distance seasonal movements. The birds are typically life long residents of relatively small tropical islands. They do, however, make periodic trips to and from historical nesting sites. Since breeding and egg laying appear to occur throughout much of the year the periodicity of movement patterns is unclear. In most cases nesting areas are probably within a short distance of year-long feeding areas, except when special thermal areas or specific beaches are used for nesting. Breeding is promiscuous with several males competing and displaying for receptive females. There are unique male breeding calls and displays, but no well-defined breeding area. Nesting probably occurs year-round but appears to peak from April through November. Micronesian megapodes incubate their eggs by burying them in a mound of soil or a mixture of soil and vegetation or by placing eggs in holes heated by geothermal activity (volcanic steam vents, hot soil near hot springs, heated volcanic cinder, etc.) especially in certain areas of the Mariana Islands north of Saipan. Successful nest sites are used repeatedly. A nesting mound or site is used by several female birds and may represent the breeding population from a large area or even the entire population on a small island. The texture and composition of substrate is important for nesting mounds. Sandy or fine grained, well-drained, forest soils are preferable to rocky or clay laden soils. A relatively open understory with a substrate of sand or loose coralline rubble seems to be preferred on Kayangel Atoll, an important nesting site. Mounds in Palau are typically located along the inland margin of sandy beaches in strand forest vegetation. Soils must be aerated well enough for gas exchange at depths of up to 22.8 in (0.75 m). The amount of solar insolation is also important in determining a site. Mounds are located in relatively open areas, usually at the base of a large dead or dying tree or along the length of a fallen trunk. Mounds may be up to 26.24 ft (8 m) in diameter and 6.5-9.8 ft (2-3 m) high. In some cases two or three mounds may be located in the same general vicinity. Some birds in the megapode family actively regulate the temperature of the mound by adding or removing material. Incubation is at least 40 days long. The total number of eggs laid by each female is unknown. Eggs are reddish brown when freshly laid; as they incubate they fade into a white color. Large mounds may yield 50-100 eggs. There is no parental care. The young chicks are completely precocial. When the chicks reach the surface they can fly and walk and feed themselves. Micronesian megapode is an omnivorous gallinaceous bird that feeds on seeds, small fruits, plant shoots, insects, snails, millipedes, worms, crabs, and grit found on and picked from the forest floor. They forage in a chicken-like manner scratching for food in leaf litter and other forest detritus as they walk along the ground. Micronesian megapode is either heard or observed walking and/or foraging for food throughout all periods of the day. They appear to be more active in early morning and late afternoon hours. They roost in the late afternoon or evening at heights of 6.5-13 ft (2-4 m) off the ground in shrubs or trees. During the nesting season, the birds are most active during the early morning near nest mounds.

Habitat

Micronesian megapode occurs in tropical, broadleaf, evergreen forests. It forages on the forest floor and roosts in trees or bushes. It is associated with native forests in Palau and the Mariana Islands. More specifically the birds frequent limestone forests, beach-strand forests, and native forests on volcanic soils. This species prefers a relatively open understory forest for feeding and nesting.

On Agiguan and Saipan (Marianas) the birds inhabit native limestone forests at the base of, or near, limestone cliffs. Dominant plant species include an overstory of large trees (Pisonia grandis, Erythrina variegata, Neisosperma oppositifolia, Albizia lebbeck, Ficus prolixa ) and a rich understory of trees, shrubs and vines (Cynometra ramiflora, Guamia mariannae, Cordia subcordata, Morinda citrifolia, Carica papaya, Entada pursaetha, Abrus precatoris ). The forest floor is relatively open and rocky with open areas of leaf litter and bare soil. The ground is heavily shaded. Individuals apparently forage primarily in small patches of native forest that may include many of the above species plus others. In the Marianas and Palau they are also associated with beach-strand forests for feeding and most notably nesting. In Palau the bird is found primarily on the small, isolated, limestone "rock islands" from Koror to Peleliu. This is heavily forested, rugged terrain, with practically no soil. Birds tend to concentrate near nest sites, generally near small sandy, forested beaches. Dominant plants of the narrow beach line strand forest include Messerschmidia argentea, Scaevola taccada, Ipomoea pescaprae, and Hernandia sonora. Favorite foraging areas include the sandy vegetated flats behind the beaches and the base of cliffs along the flats. A more open, rather than extremely dense understory seems to be preferred. They are found less commonly toward the interior of the limestone islands, where they forage in the scattered pockets of soil among the jagged rocks and along the base of scarps. On the large volcanic island of Babeldoab they are rare. Here they are found at widely scattered locations in deep forest, generally where the understory is relatively open. A few nest sites located on Babeldoab in 1977-1979 were toward the mouths of larger river valleys. In Palau, the greatest densities were found to be on the low sandy islet of Ngeriungs at Kayangel Atoll. This islet is uninhabited, and the substrate consists of sand interspersed with loose coralline rubble. The islet supports atoll strand vegetation with a relatively open understory. There are large colonies of nesting noddies (mostly black noddies, Anous minutus ), which may add significantly to the fertility of the island. Micronesian megapode inhabits the strand forest types throughout the year and during all life stages. There appears to be no variety in habitats related to age of the birds, although there is still more to learn about habitat relationships.

Distribution

Past distribution includes the islands/island complexes of Guam, Palau (Babelthaup, Koror, Auror, Kayangel, Garakayo, Ngesebus, Peleiu, Ngabab, Gayangas, Arumidin, and numerous unnamed "rock islands"), and the Northern Mariana Islands (Rota, Aguijan, Tinian, Saipan, Alamagan, Pagan, Agrihan, and Asuncion). The known range of the bird in Palau has apparently not decreased significantly since historic times. Micronesian megapode is reported extirpated from Guam. The species is presently known from the Northern Mariana Islands (Aguijan—also known as Agiguan and Goat Island, Saipan, Anatahan, Sarigan, Guguan, Alamagan, Tinian and Medinilla).

Threats

Subsistence harvest of eggs and adults was historically common among the native islanders and continues to a lesser extent today. This species is also valued by bird watchers. Occasionally these birds are killed by indiscriminate shooting. Beginning with the first reports in Micronesia several scientists, collectors and historians have remarked that populations of Micronesian megapode were small and/or declining and presumed the cause to be overharvesting of eggs and hunting of adults by indigenous islanders. To some extent this continues today. In Palau and the Marianas local people eat both adults and their eggs; with a preference for eggs which can be easily located and removed from large incubation mounds. Initial reports from the Marianas indicated that the birds were disappearing from several islands. In the late 1800s a visiting scientist felt that the species would probably not last much longer on Saipan and Rota owing to incessant hunting by natives. By 1935 they could not be located on Guam and only a few older residents remembered seeing and hunting the birds.

Removal of native vegetation is thought to have negatively affected the populations, particularly on the islands of Rota, Tinian, Agiguan, and Saipan, which were converted largely to sugar-cane production during the Japanese Administration. There was serious destruction of habitat by bombing and shelling during the Second World War on the Southern islands of Palau and on Tinian and Saipan in the Marianas. Shortly after the Second World War several ornithologists visiting the Marianas could not locate the birds and feared that the fighting and their use as food further depleted the population. In Palau small populations of five to 30 birds were estimated on four islands following the Second World War and hunting was still taking place. In a review of extinct and vanishing birds the cause for the probably demise of Micronesian megapode was egg predation by humans where a subsistence type economy exists. Additional existing threats at the present time include: Negative habitat effects of large populations of feral goats and pigs on several uninhabited islands; localized predation of eggs by introduced monitor lizards (Varanus indicus ); and occasional indiscriminate killing by hunters, as well as other introduced predators such as rats, cats, dogs, and pigs. A recent threat in Palau includes the development of recreational areas on the small, isolated sandy beaches where they normally nest. Also, the clearing of native forest for farming, road construction, and development projects destroys habitat. The extensive stands of introduced tangantangan (Leucaena leucocephala ) trees on some of the Mariana Islands has contributed to habitat degradation. The illegal harvest of eggs does not now appear to be a major problem in the Marianas, though eggs are still taken in Palau. Continued poaching will likely remain a threat, as will introduced predators and feral ungulates. Military training activities on Tinian may harm the birds in the future. The eventual development of cliff base and shoreline property will have a negative effect on the habitat. Already on Saipan property trades and development in the Marpi area threaten the well being of the small reintroduced population found there. The development of tourist facilities in the uninhabited northern islands may also have a negative effect on the birds if planned thoughtlessly. The rapid demand for land and development in the Marianas will eventually displace many species of wildlife, including Micronesian megapode. Resort development, especially in Palau, will also remain a threat.

Conservation and Recovery

Recovery for the existing Micronesian megapode populations will involve more research on their breeding biology, particularly on distribution of nest sites, reducing nest predation by eliminating feral (exotic) pigs and monitor lizards from megapode habitat, though this action is not feasible at present, protection from hunting and harvesting of eggs by humans, the preservation of nesting sites and the restricting of development at such sites (by proper land use zoning), the preservation of native forest habitat, increasing public awareness of their endangered status, and reintroduction of Micronesian megapode to their appropriate habitat. Habitat is presently being lost to agricultural, residential, recreational, and business development, as well as feral ungulates. Regrowth of native forests should be encouraged by removal of exotic vegetation and subsequent planting of native tree species. Because the young require no parental care, and eggs could be easily transported among islands, translocating eggs to islands where the species is now extinct would be a feasible way to re-establish populations in the Marianas. Adult birds may also be transplanted to augment existing populations. Recovery actions underway include surveys on all islands of the Marianas and a study of their dispersion and seasonality of calling.

The Commonwealth of the Northern Mariana Islands does have provisions in its regulations to list species as endangered, however, none have been listed to date. In accordance with Public Law 2-51, Second Legislature of the Commonwealth of the Northern Mariana Islands (1981), the current regulations of the Division of Fish and Wildlife prohibit the take of nongame species, including Micronesian megapode. The administering agency is the Division of Fish and Wildlife, Department of Natural Resources.

Virtually nothing is known about the population biology of this unique species. There is no data on survival rates, mortality, sex ratios, longevity or predation rates from either Palau or the Marianas. Population estimates are incomplete. Possible current limiting factors include the availability of adequate nesting sites, limited amounts of undisturbed native forest, degradation of habitat by increasing numbers of feral animals, predation by monitor lizards, illegal hunting/egg collecting, and destructive volcanic activity.

The recovery potential for Micronesian megapode is extremely good. These birds are ideal candidates for reintroduction to formerly inhabited islands and augmentation transplants to existing populations. They can be successfully collected as eggs, transported easily and hatched at new sites with little difficulty. Since they are completely precocial, young birds could colonize islands without the need for parental stock. Excellent localities for reintroduction exist on the islands of Rota and Tinian where the birds are now extinct. The small population on Aguijan and Saipan could be augmented by release of birds from the northern islands.

Contact

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

Reference

U.S. Fish and Wildlife Service. 1998. "Recovery Plan for the Micronesian Megapode (Megapodius laperouse laperouse ). U.S. Fish and Wildlife Service, Portland, Oregon. 65+pp.