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

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
-	B1ab(ii,iii,iv,v)	B1ab(ii,iii,iv,v)

Red List history

Year	Category	Criteria
2016	Endangered	B1ab(ii,iii,iv,v)
2013	Endangered	B1ab(ii,iii,iv,v)
2012	Endangered	B1ab(ii,iii,iv,v)
2011	Endangered	B1a+b(ii,iii,iv,v)
2008	Endangered	B1a+b(ii,iii,iv,v)
2004	Endangered
2000	Endangered
1996	Vulnerable
1994	Vulnerable
1988	Threatened

Migratory status	not a migrant	Forest dependency	Does not normally occur in forest
Land mass type		Average mass	-

	Estimate	Data quality
Extent of Occurrence breeding/resident (km2)	45,900	medium
Number of locations	11-100	-
Severely Fragmented		-

	Value	Data quality	Derivation	Year of estimate
No. of mature individuals	1500	medium	estimated	2002
Population trend	Decreasing	poor	suspected	-
Decline (3 years/1 generation past)		-	-	-
Decline (5 years/1 generation past)		-	-	-
Decline (10 years/1 generation past)		-	-	-
Decline (10 years/3 generation future)		-	-	-
Decline (10 years/3 generation past and future)		-	-	-
Number of subpopulations	5	-	-	-
Percentage in largest subpopulation		-	-	-
Generation length (yrs)	6.9	-	-	-

Population justification: The species's population is estimated to number c.2,200 individuals (K. Uyehara, A. Marshall and A. Engilis Jr. in litt. 2007), roughly equivalent to 1,500 mature individuals.

Trend justification: The species is suspected to be in decline owing to hybridisation, wetland loss and introduced predators, although the likely rate of decline has not been estimated.

Country/Territory	Occurrence status	Presence	Resident	Breeding	Non-breeding	Passage
USA	N	Extant	Yes

Country/Territory	IBA Name
USA	Pearl Harbor National Wildlife Refuge
USA	Kealia Pond National Wildlife Refuge
USA	Hanalei National Wildlife Refuge

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Artificial/Aquatic & Marine	Artificial/Aquatic - Ponds (below 8ha)	suitable	resident
Forest	Subtropical/Tropical Swamp	marginal	resident
Grassland	Subtropical/Tropical Seasonally Wet/Flooded	suitable	resident
Marine Coastal/Supratidal	Coastal Brackish/Saline Lagoons/Marine Lakes	suitable	resident
Wetlands (inland)	Permanent Freshwater Lakes (over 8ha)	suitable	resident
Wetlands (inland)	Permanent Freshwater Marshes/Pools (under 8ha)	suitable	resident
Wetlands (inland)	Permanent Rivers/Streams/Creeks (includes waterfalls)	major	resident
Altitude	0 - 3300 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Annual & perennial non-timber crops - Agro-industry farming	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Majority (50-90%)		Slow, Significant Declines		Past Impact
		Stresses Ecosystem degradation, Ecosystem conversion
Biological resource use	Hunting & trapping terrestrial animals - Intentional use (species is the target)	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Majority (50-90%)		Slow, Significant Declines		Past Impact
		Stresses Species mortality
Climate change & severe weather	Droughts	Timing		Scope		Severity		Impact
		Past, Likely to Return		Whole (>90%)		Rapid Declines		Past Impact
		Stresses Ecosystem degradation
Human intrusions & disturbance	Recreational activities	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Rapid Declines		Medium Impact: 7
		Stresses Species disturbance
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Anas platyrhynchos	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Rapid Declines		High Impact: 8
		Stresses Hybridisation
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Canis familiaris	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Capra hircus	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		No decline		Low Impact: 4
		Stresses Ecosystem degradation
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Felis catus	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Herpestes javanicus_old	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Named species	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Reduced reproductive success
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Sus domesticus	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		No decline		Low Impact: 4
		Stresses Ecosystem degradation
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Unspecified species	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Rapid Declines		High Impact: 8
		Stresses Hybridisation
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Unspecified species	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation
Natural system modifications	Other ecosystem modifications	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Minority (<50%)		Unknown		Past Impact
		Stresses Ecosystem conversion
Residential & commercial development	Housing & urban areas	Timing		Scope		Severity		Impact
		Past, Unlikely to Return		Minority (<50%)		Slow, Significant Declines		Past Impact
		Stresses Ecosystem degradation, Ecosystem conversion

Purpose	Primary form used	Life stage used	Source	Scale	Level	Timing
Food - human	-	-			Non-trivial	Recent
Pets/display animals, horticulture	-	-		International	Non-trivial	Recent

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Recommended citation
BirdLife International (2023) Species factsheet: Anas wyvilliana. Downloaded from http://www.birdlife.org on 31/03/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 31/03/2023.