• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Taxonomic note
Hypotaenidia owstoni (del Hoyo and Collar 2014) was previously placed in the genus Gallirallus.

Taxonomic source(s)
del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non-passerines. Lynx Edicions BirdLife International, Barcelona, Spain and Cambridge, UK.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
D	D	D1+2

Red List history

Year	Category	Criteria
2019	Critically Endangered	D
2016	Extinct in the Wild
2012	Extinct in the Wild
2010	Extinct in the Wild
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
1988	Threatened

Migratory status	not a migrant	Forest dependency	low
Land-mass type		Average mass	-

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	4 km2	medium
Area of Occupancy (breeding/resident)	4 km2
Number of locations	1	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	1-49 mature individuals	poor	suspected	2019
Population trend	increasing	-	suspected	-
Generation length	3.4 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: Although individuals have been released on Guam and on Rota, there are unlikely to be any wild individuals remaining on Guam and the population on Rota is not yet considered to be self-sustaining. Sixteen birds were released on Cocos Island in 2010, with a further 10 in 2012 (The Lost Bird Project Inc. 2013). Evidence for breeding has been observed, and the bird is now found throughout the island, where it is considered to be self-sustaining. The population size on Cocos has not been estimated, but the area of the island is only c.38 hectares so the population size is likely to be extremely small (F. Amidon in litt. 2012, S. Medina in litt. 2017). The population is therefore placed in the band 1-49 mature individuals.

Trend justification: The species was formerly extinct in the wild and an introduced population has now been established on Cocos, where 16 individuals were released in 2010 and a further 10 in 2012 (The Lost Bird Project Inc. 2013). Although there are no population data from which to estimate a trend, evidence for breeding has been observed and the bird is now found throughout the island, so the population size is suspected to be increasing.

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Guam (to USA)	extant	native	yes

Country/Territory	IBA Name
Guam (to USA)	Cocos Island, Guam
Guam (to USA)	Guam National Wildlife Refuge

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Artificial/Terrestrial	Pastureland	suitable	resident
Artificial/Terrestrial	Plantations	suitable	resident
Forest	Subtropical/Tropical Moist Lowland	suitable	resident
Grassland	Subtropical/Tropical Dry	major	resident
Savanna	Dry	suitable	resident
Shrubland	Subtropical/Tropical Dry	major	resident
Altitude		Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Annual & perennial non-timber crops - Scale Unknown/Unrecorded	Timing		Scope		Severity		Impact
		Future		Majority (50-90%)		Unknown		Unknown
		Stresses Ecosystem degradation, Ecosystem conversion
Climate change & severe weather	Storms & flooding	Timing		Scope		Severity		Impact
		Future		Whole (>90%)		Rapid Declines		Medium Impact: 6
		Stresses Ecosystem degradation, Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Boiga irregularis	Timing		Scope		Severity		Impact
		Past, Likely to Return		Whole (>90%)		Rapid Declines		Past Impact
		Stresses Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Felis catus	Timing		Scope		Severity		Impact
		Past, Likely to Return		Majority (50-90%)		Rapid Declines		Past Impact
		Stresses Reduced reproductive success, Species mortality
Natural system modifications	Fire & fire suppression - Increase in fire frequency/intensity	Timing		Scope		Severity		Impact
		Future		Majority (50-90%)		Slow, Significant Declines		Low Impact: 4
		Stresses Ecosystem degradation, Reduced reproductive success, Species mortality
Residential & commercial development	Housing & urban areas	Timing		Scope		Severity		Impact
		Future		Majority (50-90%)		Unknown		Unknown
		Stresses Ecosystem degradation, Ecosystem conversion

Purpose	Scale
Pets/display animals, horticulture	international

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Recommended citation
BirdLife International (2024) Species factsheet: Guam Rail Hypotaenidia owstoni. Downloaded from https://datazone.birdlife.org/species/factsheet/guam-rail-hypotaenidia-owstoni on 26/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 26/12/2024.