Guam rail - WikiHQ

The Guam rail (Gallirallus owstoni), known locally and in Chamorro as ko'ko, is a small, terrestrial bird endemic to Guam in the Rallidae family. They are one of the island's few remaining endemic bird species. The species became extinct in the wild in the early 1980s when biologists captured the remaining wild population to establish a breeding program. They have since been successfully introduced to the nearby Rota and Cocos islands.

Adult male and female plumage is primarily brown with barred black-and-white plumage on their underside. Their heads are brown with a grey stripe running above the eye and a medium-length grey bill. They have strong legs with long toes that help them walk over marshy ground. Their most common vocalizations are short "kip" notes, but also screeches during the breeding season.

Guam rail numbers fell drastically due to predation by invasive brown tree snakes. The species is now being bred in captivity by the Division of Aquatic and Wildlife Resources on Guam, and at some mainland U.S. zoos. Since 1995, more than 100 rails have been introduced on the island of Rota in the Commonwealth of the Northern Mariana Islands, in an attempt to establish a wild breeding colony. In 2010, 16 birds were released onto Cocos Island, with 12 more being introduced in 2012. The generic name, Hypotaenidia, comes from the Ancient Greek meaning "under" and meaning "stripe" or "band." This refers to the banded feathers seen on their underside and wings, typically found across rail species. The Guam rail is now placed in the genus Gallirallus that was introduced in 1841 by Frédéric de Lafresnaye.

Description

Guam rails are a medium-sized rail species, growing to about 11 inches (28 cm) in total length. Adults will weigh around 7 to 12 ounces (200 to 350 grams).

Adult Guam rails are monomorphic, meaning males and females have the same plumage and characteristics. They are primarily brown, with a grey bill and tan-colored legs. 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.

Today, the rail is still found on Guam, though in captivity, with wild populations introduced on Rota and Cocos Islands. Since 1985, the rails have only lived in captivity on Guam, located at the Guam Department of Agriculture.

Ecology and behavior

Guam rails are secretive, fast birds. Though they are capable of a short bursts of flight, they seldom fly. 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.

Breeding

It is a year-round ground nester and lays 2–4 eggs per clutch, and both parents share in the construction of a shallow nest of leaves and grass. They mature at six months of age, and have been known to produce up to 10 clutches per year in captivity.

Their nesting habits make them highly susceptible to predators, such as the native Mariana monitor and the invasive feral pig, feral cat, feral dog, mangrove monitor, brown tree snake, black rat, and Norway rat.

Food and feeding

Guam rails are omnivorous foragers known to consume gastropods, insects, geckos, seeds, and vegetable matter.

Guam rails have been observed foraging and hunting. When foraging, they peck food from the ground and eat seeds and flowers from grasses. They have also been observed hunting insects, particularly butterflies. 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.

Threats

left|thumb|A brown tree snake on a barbed wire fence.

The brown tree snake (Boiga irregularis) is one of the primary threats to the survival of the Guam rail and the introduction of the snake has been catastrophic for Guam's biodiversity. The snake was likely passively introduced to the island as a stowaway in a military cargo ship after World War II. Once introduced to Guam, the snakes thrived off an abundance of prey lacking natural predators. Brown tree snakes are opportunistic feeders and have been observed on Guam consuming lizards, birds, eggs, insects, small mammals, and human trash. The snake is nocturnal, arboreal, and adept at preying on roosting or nesting birds and their offspring.

Over time, the snake decimated the other native avifauna in Guam's forests. With less prey found in the trees, it took advantage of the nests of the Guam rail, found on the forest floor. It is unlikely the snakes could prey on the larger adult rails, instead feeding on the eggs and nestlings.

Invasive ungulates, including feral pigs and Philippine deer, destroy native forests and consequently, Guam rail habitat. Their behaviors contribute to the decline of Guam's forests by trampling vegetation and rooting for food. In addition to this, feral pigs wallowing and deer thinning the forest canopy contribute to the ecosystem's disruption. These factors combined have contributed to altered soil properties, forest ecology, and decreases in groundcover.

Feral cats have also proven to be a major barrier to successfully reintroducing the species to Guam. Following the reintroduction of Guam rails at Andersen Air Force Base in 2006, feral cats killed all of the introduced birds within eight weeks.

Conservation

thumb|Ceremonial statue of a Guam rail (ko'ko), presented as a gift by the Government of Guam.

Decline

The species was once abundant, with an estimated population between 60,000 and 80,000 in the late 1960s and early 1970s.

Beck was also a driving force in establishing Guam rail breeding programs in zoos throughout the mainland United States. These initially began with just three zoos in the U.S.—the Bronx Zoo, the Philadelphia Zoo, and the National Zoo in Washington, D.C.—and was soon expanded to other zoos.

The efforts by Beck, and others, to save the species proved successful. By the time of Beck's death in 2008 there were approximately 120 Guam rails in captivity in Guam, and another 35 birds were in captive breeding programs throughout the U.S. at a total of 17 zoos then participating – 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.

In November 2010, sixteen Guam rails were released on Cocos Island, a 33 hectare atoll located 1 mile off 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 biosecurity measures.

In culture

Guam's symbolic bird is the Ko'ko'.

Ko'ko' Road Race Weekend is hosted every year on Guam to raise awareness of the species and conservation efforts.

References

External links

BirdLife Species Factsheet
USGS: Extinctions and Loss of Species from Guam: Birds