Guam rail

Guam rail
At the Cincinnati Zoo
Conservation status
Critically Endangered  (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Gruiformes
Family:	Rallidae
Genus:	Hypotaenidia
Species:	H. owstoni
Binomial name
Hypotaenidia owstoni Rothschild, 1895
Synonyms
Rallus owstoni (Rothschild, 1895) Gallirallus owstoni (Rothschild, 1895)

The Guam rail (Hypotaenidia owstoni), known in Chamorro as ko'ko', is a small, terrestrial bird in the Rallidae family. It is endemic of the island of Guam, and is 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. They have since been successfully reintroduced to Guam and introduced to the nearby Rota and Cocos islands. In 2019, the species became the second bird after the California condor to be reclassified by the IUCN from extinct in the wild to critically endangered.

Adult male and female Guam rails are 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.

Taxonomy and etymology

The Guam rail was first described as Hypotaenidia owstoni in 1895 by Lord Walter Rothschild. Rothschild announced the specific name owstoni was "in honour of Mr. Alan Owston, of Yokohama, whose men have collected for me on the Marianne Islands." The generic name, Hypotaenidia, comes from the Ancient Greek hypo meaning "under" and tainia meaning "stripe" or "band"

Hypotaenidia   Okinawa rail  Barred rail  New Britain rail  Bar-winged rail  Bougainville rail  Santa Isabel rail  Guadalcanal rail  Roviana rail  Guam rail  Wake rail  Dieffenbach's rail  Lord Howe Woodhen  Buff-banded rail  Tahiti rail

Cladogram of the genus Hypotaenidia

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). They have an elongated body, with small wings and medium-length legs. Guam rails have underdeveloped wing muscles and are considered flightless, though they can fly about 3 to 10 feet (1 to 3 meters) at once. Their strong leg muscles make them fast runners instead.

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.

Distribution and habitat

The Guam rail is endemic to and only found on Guam in the Mariana Islands. Guam covers 212 square miles (549 square kilometers) and has a tropical rainforest climate. The rails were once distributed widely across most habitats on the island, including mixed forest, savanna, grasslands, fern thickets and agricultural areas. Individuals observed by the Guam Division of Aquatic and Wildlife Resources were noted as preferring edge habitats that provided good cover.

Following the introduction of the brown tree snake sometime after World War II, the Guam rail population precipitously declined. The species was extirpated from the island when in 1985, the few remaining individuals were collected by biologists for the establishment of a conservation program. The program has proven successful, and three populations have been established. Two wild populations exist on Cocos Island and Rota, while a third captive population is located at the Guam Department of Agriculture.

Behavior and ecology

Guam rails are secretive and can run rapidly. Though 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, making it 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. It lays 2–4 eggs, 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.

Food and feeding

Guam rails are omnivores known to consume gastropods, insects, geckos, seeds, and vegetable matter. It is omnivorous, but appears to prefer animals over vegetable food.

Parasites

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.

Threats

The species was once abundant, with an estimated population to be around 70,000 before the 1960s. It evolved in the absence of predators, such as snakes and rats, and might have been more abundant before American colonization. After the end of World War II, the brown tree snake was accidentally transported from its native range in Papua New Guinea to Guam, probably as a stowaway in military ship cargo. Beginning in the 1960s, the snake became well established as numbers began to grow exponentially, and the rail populations subsequently plummeted, along with the rest of Guam's native avifauna. The Guam rail had no experience with such a predator, and lacked protective behaviors against the snake. Consequently, it was an easy prey for this efficient, nocturnal predator.

Appreciable losses of the Guam rail was not evident until the mid 1960s. By 1963, several formerly abundant rails had disappeared from the central part of the island where snakes were most populous. By the late 1960s, it had begun to decline in the central and southern parts of the island, and remained abundant only in isolated patches of forest on the northern end of the island. Snakes began affecting the rail in the north-central and extreme northern parts of the island in the 1970s and 1980s, respectively. The population declined severely from 1969 to 1973, and continued to decline until the mid 1980s. It was last seen in the wild in 1987. Other significant threats to the rail include habitat destruction, predation by introduced rats, feral cats, and pigs.

Conservation efforts

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

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.

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.

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.

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."

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.

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.

External links

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