Guamralle

Bestimmung

It is a medium-sized rail, about 11 inches (28 cm) in total length. The body is elongated and laterally compressed, particularly in the neck and breast regions. The plumage or feather color and pattern of both sexes is similar, however, males can often be distinguished by their larger size. The head and back are brown. It has a grey eye stripe and throat, a dark blackish breast with white barring, and the legs and beak are dark brown.

Taxonomie

Wissenschaftlicher Name

Gallirallus owstoni

Autorität

Rothschild, 1895

Ordnung

Gruiformes

Familie

Rallidae

Gattung

Gallirallus

Verbreitung und Lebensraum

Zugverhalten

Resident species

Verhalten

It is secretive and it can run rapidly. Though capable of a short bursts of flight, the bird seldom flies. It was found more frequently in savannas and scrubby mixed forest than in uniform tracts of mature forest. It was usually found in dense vegetation but it was also observed bathing or feeding along roadsides or forest edges. Its call is a loud, piercing whistle or series of whistles, usually given by two or more birds in response to a loud noise, the call of another rail, or other disturbances. Though individuals will respond almost invariably to the call of another rail, the species is generally silent. It is omnivorous, but appears to prefer animals over vegetable food. It is known to eat gastropods, skinks, geckos, insects, and carrion, as well as seeds and palm leaves.<p>The species hosted a unique louse, Rallicola guami, which seems to have been a victim of conservation-induced extinction, since Guam rails taken into captivity were deloused to assist survival; it is considered most likely extinct.

Schutzstatus

Nine of the eleven species of native forest-dwelling birds have been extirpated from Guam. Five of these were endemic at the species or subspecies level, and are now extinct. Two of these species, the Guam rail and the Guam kingfisher, are being captively bred in zoos, in the hope that they can eventually be released back into the wild. Several other native species exist in precariously small numbers, and their future on Guam is perilous. Most native forest species, including the Guam rail, were virtually extinct when they were listed as threatened or endangered by the U.S. Fish and Wildlife Service in 1984.<p>Zoologist Bob Beck, a wildlife supervisor with the Guam Department of Agriculture's Division of Aquatic and Wildlife Resources, is credited with leading the efforts to capture the remaining wild Guam rails, Guam kingfishers, and other native birds to save them from extinction. His efforts to save the Guam rail began in 1982, and lasted more than 20 years. Beck was considered to be instrumental in capturing the remaining population of Guam rails, and establishing captive breeding programs for the species on Guam. He later established a release site and an introduced breeding population of Guam rails on the neighboring island of Rota in the Northern Mariana Islands.<p>Beck was also a driving force in establishing Guam rail breeding programs in zoos throughout the mainland United States. Beck's Guam rail breeding program initially began with just three zoos in the U.S.—the Bronx Zoo, the Philadelphia Zoo, and the National Zoo in Washington, D.C. The program proved to be successful, and was soon expanded to include other zoos. As of 2008, seventeen zoos now participate in the Guam rail breeding program, including: the Audubon Zoo in New Orleans, the San Diego Zoo, the Santa Fe College Teaching Zoo, and zoos in Chicago, Houston, and San Antonio.<p>The efforts by Beck, and others, to save the Guam rail have been promising. There are now approximately 120 Guam rails in captivity in Guam, and approximately 35 birds in captive breeding programs throughout the United States. Biologist Gary Wiles, who worked on the Guam rail breeding program from 1981 through 2000, said of Beck's efforts to save the Guam rail, "Bob was one of the first to begin organizing catching the birds, so they could be brought into captivity, held there, and bred. He started a captive population. We still have Guam rails today because of his efforts." Suzanne Medina, a wildlife biologist, also credited Beck with saving the Guam rail, "Bob Beck was the ko'ko' champion; [he] was Guam's champion at the time for preventing the extinction of these birds."<p>A recent effort to introduce rails on Guam in a 22 hectare forested area concentrated on protecting the rails by limiting snakes using a combination of trapping and a perimeter barrier to reduce re-invasion by snakes. This endeavor allowed the tentative survival of several pairs of rails released into the area. Reproduction by the rails was reported in this control area on the basis of sounds attributed to chicks. The preliminary success constitutes one of the few bright spots in the conservation of Guam's native fauna in recent years, and speaks to future opportunities to recover wildlife.<p>In November 2010, sixteen Guam rails were released on Cocos Island, a 33 hectare small atoll located 1 mile off the coast of the southern tip of Guam, as part of its reintroduction two decades after its extinction in the wild. It was an effort to provide safe nesting areas for the rails, as well as a place for the public to see them in the wild. Before the reintroduction, rats were eradicated off the island, and the forest was further enhanced with native trees. A native lizard survey was conducted to make sure that the rails had enough food to eat. Monitor lizard populations were reduced to minimize their impacts on the newly released rails. The reintroduction proved to be successful, as evidence of breeding has been observed. This will provide a model environment to develop strategies for future reintroductions, as well as expertise in rodent and snake detection, eradication, and bio-security measures.

Bestandstrend

rising