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The Guam rail (''Hypotaenidia owstoni''), known locally and in Chamorro as ''ko'ko, is a small, terrestrial
bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
endemic to Guam in the Rallidae family. They are one of the island's few remaining
endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...
bird species. The species became
extinct in the wild A species that is extinct in the wild (EW) is one that has been categorized by the International Union for Conservation of Nature as only consisting of living members kept in captivity or as a naturalized population outside its historic range ...
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. In 2019, they became the second bird species to be reclassified by the
International Union for the Conservation of Nature The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...
from Extinct in the Wild to
Critically Endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...
. 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 treesnakes. 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 The Northern Mariana Islands, officially the Commonwealth of the Northern Mariana Islands (CNMI), is an unincorporated territory and commonwealth of the United States consisting of 14 islands in the northwestern Pacific Ocean.Lin, Tom C.W.Amer ...
, in an attempt to establish a wild breeding colony. In 2010, 16 birds were released onto
Cocos Island Cocos Island () is a volcanic island in the Pacific Ocean administered by Costa Rica, approximately southwest of the Costa Rican mainland. It constitutes the 11th of the 15 districts of Puntarenas Canton of the Puntarenas Province, Province of ...
, 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 meaning "under" and meaning "stripe" or "band." This refers to the banded feathers seen on their underside and wings, typically found across rail species.


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 Flightless birds are birds that cannot fly, as they have, through evolution, lost the ability to. There are over 60 extant species, including the well-known ratites ( ostriches, emus, cassowaries, rheas, and kiwis) and penguins. The smal ...
, 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 Plumage () is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, there can b ...
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

Historically, the rail was only found on the island of Guam. 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. Guam is an island covering about 132,230 acres. According to a 2013 survey, about 53% of the island is forested. The climate is tropical marine, with little change in temperature throughout the year and a dry season lasting from January until May. 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.


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 A feral pig is a domestic pig The pig (''Sus domesticus''), also called swine (: swine) or hog, is an omnivorous, domesticated, even-toed, hoofed mammal. It is named the domestic pig when distinguishing it from other members of the g ...
,
feral cat A feral cat or a stray cat is an unowned domestic cat (''Felis catus'') that lives outdoors and avoids human contact; it does not allow itself to be handled or touched, and usually remains hidden from humans. Feral cats may breed over dozens ...
, feral dog, mangrove monitor,
brown tree snake The brown tree snake (''Boiga irregularis''), also known as the brown catsnake, is an arboreal rear-fanged colubrid snake native to eastern and northern coastal Australia, eastern Indonesia (Sulawesi to Papua), Papua New Guinea, and many island ...
,
black rat The black rat (''Rattus rattus''), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus ''Rattus'', in the subfamily Murinae. It likely originated in the Indian subcontinent, but is n ...
, and Norway rat.


Food and feeding

Guam rails are omnivorous foragers known to consume
gastropods Gastropods (), commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and from the land. Ther ...
,
insects Insects (from Latin ') are hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed ...
,
geckos Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder Gekkota, geckos are found in warm climates. They range from . Geckos are unique among lizards f ...
, seeds, and vegetable matter. A large part of their diet consists of giant African snails, which were introduced to Guam around 1945 and became an easy food source for the birds. Pieces of
snail shell The gastropod shell is part of the body of many gastropods, including snails, a kind of mollusc. The shell is an exoskeleton, which protects from predators, mechanical damage, and dehydration, but also serves for muscle attachment and calcium ...
and
coral Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...
have been found in the stomach and
gizzard The gizzard, also referred to as the ventriculus, gastric mill, and gigerium, is an organ found in the digestive tract of some animals, including archosaurs (birds and other dinosaurs, crocodiles, alligators, pterosaurs), earthworms, some gast ...
contents of Guam rails, suggesting use as grit. 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.


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 Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
.


Threats

The brown treesnake (''Boiga irregularis'') is one of the primary threats to the survival of the Guam rail; 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, it thrived with an abundance of prey lacking natural predators. The snake is an
opportunistic feeder Feeding is the process by which organisms, typically animals, obtain food. Terminology often uses either the suffixes -vore, -vory, or -vorous from Latin ''vorare'', meaning "to devour", or -phage, -phagy, or -phagous from Greek φαγε ...
, and on Guam has been observed to consume lizards, birds, eggs, insects, small mammals, and human trash. The snake is nocturnal and arboreal and adept at preying on roosting and nesting birds and their offspring. Over time, the snake decimated the populations of other native
avifauna Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight ...
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 pig A feral pig is a domestic pig The pig (''Sus domesticus''), also called swine (: swine) or hog, is an omnivorous, domesticated, even-toed, hoofed mammal. It is named the domestic pig when distinguishing it from other members of the g ...
s 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 Wallowing in animals is Comfort behaviour in animals, comfort behaviour during which an animal rolls about or lies in mud, water or snow. Some definitions include rolling about in dust, however, in ethology this is usually referred to as dust bat ...
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


Decline

The species was once abundant, with an estimated population between 60,000 and 80,000 in the late 1960s and early 1970s. 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. The Guam rail and the Guam kingfisher, are bred in captivity with hope that they may 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. 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.


Conservation efforts

Zoologist Zoology ( , ) is the scientific study of animals. Its studies include the structure, embryology, classification, habits, and distribution of all animals, both living and extinct, and how they interact with their ecosystems. Zoology is one ...
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 Captive breeding, also known as captive propagation, is the process of keeping plants or animals in controlled environments, such as wildlife reserves, zoos, Botanical garden, botanic gardens, and other Conservation biology, conservation facilitie ...
programs for the species on Guam. He later established a release site and an introduced a breeding population of Guam rails on the neighboring island of Rota in the
Northern Mariana Islands The Northern Mariana Islands, officially the Commonwealth of the Northern Mariana Islands (CNMI), is an Territories of the United States, unincorporated territory and Commonwealth (U.S. insular area), commonwealth of the United States consistin ...
. Beck was also a driving force in establishing Guam rail breeding programs in zoos throughout the mainland
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
. These initially began with just three zoos in the U.S.—the
Bronx Zoo The Bronx Zoo (also historically the Bronx Zoological Park and the Bronx Zoological Gardens) is a zoo within Bronx Park in the Bronx, New York City. It is one of the largest zoos in the United States by area and the largest Metropolis, metropol ...
, the
Philadelphia Zoo The Philadelphia Zoo is a zoo located in the Centennial District of Philadelphia on the west bank of the Schuylkill River. It was the first true zoo in the United States; it was chartered by the Commonwealth of Pennsylvania on March 21, 1859 ...
, 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 New Orleans (commonly known as NOLA or The Big Easy among other nicknames) is a Consolidated city-county, consolidated city-parish located along the Mississippi River in the U.S. state of Louisiana. With a population of 383,997 at the 2020 ...
, the
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, the Santa Fe College Teaching Zoo, and zoos in
Chicago Chicago is the List of municipalities in Illinois, most populous city in the U.S. state of Illinois and in the Midwestern United States. With a population of 2,746,388, as of the 2020 United States census, 2020 census, it is the List of Unite ...
,
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, and
San Antonio San Antonio ( ; Spanish for " Saint Anthony") is a city in the U.S. state of Texas and the most populous city in Greater San Antonio. San Antonio is the third-largest metropolitan area in Texas and the 24th-largest metropolitan area in the ...
. By 2019, the numbers of Guam rails surviving in South Pacific habitats near Guam had increased to 200 birds on Rota as well as another 60 to 80 birds on Cocos Island, where releases had taken place since the introduction of 16 birds in late 2010. Biologist Gary Wiles, who worked on the Guam rail breeding program from 1981 to 2000, said of Beck's work in helping to save the species: "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; ewas Guam's champion at the time for preventing the extinction of these birds." The
U.S. Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on March ...
and U.S. Fish & Wildlife Service have worked in collaboration with the
Department of Defense The United States Department of Defense (DoD, USDOD, or DOD) is an executive department of the U.S. federal government charged with coordinating and supervising the six U.S. armed services: the Army, Navy, Marines, Air Force, Space Force, ...
and territorial government since the 1990s to control and mitigate the brown tree snake population and assist in efforts to reintroduce the rail and other bird species to Guam. In November 2010, sixteen Guam rails were released on
Cocos Island Cocos Island () is a volcanic island in the Pacific Ocean administered by Costa Rica, approximately southwest of the Costa Rican mainland. It constitutes the 11th of the 15 districts of Puntarenas Canton of the Puntarenas Province, Province of ...
, a 33 hectare
atoll An atoll () is a ring-shaped island, including a coral rim that encircles a lagoon. There may be coral islands or cays on the rim. Atolls are located in warm tropical or subtropical parts of the oceans and seas where corals can develop. Most ...
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 bio-security 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.


See also

* Bob Beck * List of birds of Guam * List of birds of the Northern Mariana Islands


References


External links


BirdLife Species Factsheet

USGS: Extinctions and Loss of Species from Guam: Birds
{{Taxonbar, from=Q924911 Hypotaenidia Flightless birds Birds of Guam ESA endangered species Birds described in 1895 Taxa named by Walter Rothschild Critically endangered fauna of the United States