Gallirallus owstoni

Taxonomy

Assessment Information

Geographic Range

Habitat and Ecology

Threats

Conservation Actions

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Taxonomy [top]

Kingdom	Phylum	Class	Order	Family
ANIMALIA	CHORDATA	AVES	GRUIFORMES	RALLIDAE

Scientific Name:

Gallirallus owstoni

Species Authority:

(Rothschild, 1895)

Common Name/s:

English

–

Guam Rail

Assessment Information [top]

Red List Category & Criteria:

Extinct in the Wild ver 3.1

Year Assessed:

2010

Assessor/s:

BirdLife International

Reviewer/s:

Symes, A., Butchart, S.

Contributor/s:

Wiles, G., Amidon, F., Lepson, J., Wenninger, P.

Justification:
The last individual in the wild of this species died in 1987 following catastrophic declines owing to predation by the introduced brown tree-snake. A captive population survives in a snake-proof enclosure, and it breeds well in captivity. It remains classified as Extinct in the Wild until an introduced population becomes firmly established.

History:

2008	–	Extinct in the Wild
2004	–	Extinct in the Wild
2000	–	Extinct in the Wild
1996	–	Extinct in the Wild
1994	–	Extinct in the Wild

Geographic Range [top]

Range Description:	Gallirallus owstoni is endemic to Guam (to USA), where it was widely distributed until 1968 when, along with most other indigenous species, it started to decline⁴. In 1981, the population was estimated at c.2,000, in 1983 it was reckoned to number fewer than 100 and, by 1987, it was extirpated from the wild⁹. It survives in captive-breeding facilities in Guam and in 14 zoos in the USA (c.180 birds in total)¹. It was reintroduced to Guam in 1998 but a rapid population decline was observed during 2000-2002 and no rails have been detected since, either in the predator free zone (Area 50, 24 hectares) or the snake reduced open landscape¹⁰. From 1989-2007 853 captive reared rails were released on nearby Rota, Northern Mariana Islands (to USA), though this has experienced mixed success, with some populations rapidly declining to extinction, there is currently an expanding population of 40-60 individuals in the Duge area and another of 20 birds at Apanon¹⁰.
Countries:	Introduced: Northern Mariana Islands

Range Description:

Gallirallus owstoni is endemic to Guam (to USA), where it was widely distributed until 1968 when, along with most other indigenous species, it started to decline⁴. In 1981, the population was estimated at c.2,000, in 1983 it was reckoned to number fewer than 100 and, by 1987, it was extirpated from the wild⁹. It survives in captive-breeding facilities in Guam and in 14 zoos in the USA (c.180 birds in total)¹. It was reintroduced to Guam in 1998 but a rapid population decline was observed during 2000-2002 and no rails have been detected since, either in the predator free zone (Area 50, 24 hectares) or the snake reduced open landscape¹⁰. From 1989-2007 853 captive reared rails were released on nearby Rota, Northern Mariana Islands (to USA), though this has experienced mixed success, with some populations rapidly declining to extinction, there is currently an expanding population of 40-60 individuals in the Duge area and another of 20 birds at Apanon¹⁰.

Countries:

Introduced:

Northern Mariana Islands

Habitat and Ecology [top]

Habitat and Ecology:	This flightless species was widely distributed in most habitats on Guam, including forest, savanna, scrub, secondary grassland, fern thickets and agricultural areas⁵ (but not in freshwater wetland habitats⁸). It foraged along field edges and roadsides (never far from cover) for snails, slugs, insects, geckos, vegetable matter, seeds and flowers from low grasses and shrubs, and also the introduced giant African snail Achatina fulica which became an important part of the diet⁷. It breeds throughout the year (birds attaining sexual maturity at four months) with a peak period during the rains in July-November². Nests are located on dry ground in dense grass, and clutch-size is 1-4, usually 3-4⁷.
Systems:	Terrestrial

Habitat and Ecology:

This flightless species was widely distributed in most habitats on Guam, including forest, savanna, scrub, secondary grassland, fern thickets and agricultural areas⁵ (but not in freshwater wetland habitats⁸). It foraged along field edges and roadsides (never far from cover) for snails, slugs, insects, geckos, vegetable matter, seeds and flowers from low grasses and shrubs, and also the introduced giant African snail Achatina fulica which became an important part of the diet⁷. It breeds throughout the year (birds attaining sexual maturity at four months) with a peak period during the rains in July-November². Nests are located on dry ground in dense grass, and clutch-size is 1-4, usually 3-4⁷.

Systems:

Terrestrial

Threats [top]

Major Threat(s):	Its decline and extinction in the wild is the result of predation by the introduced brown tree snake Boiga irregularis⁶. Reasons for the failure of some of the introduction attempts on Rota are not known, but predation by feral cats was responsible for the failure of the reintroduction attempts on Guam¹⁰.

Major Threat(s):

Its decline and extinction in the wild is the result of predation by the introduced brown tree snake Boiga irregularis⁶. Reasons for the failure of some of the introduction attempts on Rota are not known, but predation by feral cats was responsible for the failure of the reintroduction attempts on Guam¹⁰.

Conservation Actions [top]

Conservation Actions:	Conservation Actions Underway Captive breeding started in 1984. Since 1987, efforts have been under way to establish a self-sustaining, experimental population on the nearby snake-free island of Rota^2. In 1999, birds bred there for the first time¹; birds have since been released at four sites and success has been mixed¹⁰. In late 1998, some captive-reared birds were released in northern Guam, into a small area (24 ha) protected from snakes by a barrier and trapping, and though these birds were breeding¹, this population is now extinct¹⁰. Conservation Actions Proposed Continue the captive-breeding programme. Control B. irregularis in additional areas on Guam so that more introductions can take place¹. Continue to manage the released populations on Rota to maximise the retention of the species's genetic diversity¹. Implement stringent measures to prevent the spread of B. irregularis from Guam to Rota. Before considering another reintroduction to Guam, control feral cats.

Conservation Actions:

Conservation Actions Underway
Captive breeding started in 1984. Since 1987, efforts have been under way to establish a self-sustaining, experimental population on the nearby snake-free island of Rota^2. In 1999, birds bred there for the first time¹; birds have since been released at four sites and success has been mixed¹⁰. In late 1998, some captive-reared birds were released in northern Guam, into a small area (24 ha) protected from snakes by a barrier and trapping, and though these birds were breeding¹, this population is now extinct¹⁰.

Conservation Actions Proposed
Continue the captive-breeding programme. Control B. irregularis in additional areas on Guam so that more introductions can take place¹. Continue to manage the released populations on Rota to maximise the retention of the species's genetic diversity¹. Implement stringent measures to prevent the spread of B. irregularis from Guam to Rota. Before considering another reintroduction to Guam, control feral cats.

Citation:	BirdLife International 2010. Gallirallus owstoni. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 08 February 2012.
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