• 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., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
-	-	C2a(i)

Red List history

Year	Category	Criteria
2023	Vulnerable	C2a(i)
2016	Endangered	B1ab(i,ii,iii,iv,v)
2012	Endangered	B1ab(i,ii,iii,iv,v)
2011	Endangered	B1a+b(i,ii,iii,iv); C2a(i)
2008	Not Recognised
2004	Not Recognised
2000	Not Recognised
1994	Not Recognised
1988	Not Recognised

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

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	675 km2	good
Area of Occupancy (breeding/resident)	248 km2
Number of locations	11-20	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	1261 mature individuals	good	estimated	2012
Population trend	decreasing	poor	inferred	-
Generation length	5.23 years	-	-	-
Number of subpopulations	16-20	-	-	-
Percentage of mature individuals in largest subpopulation	40%	-	-	-

Population justification: The total population was estimated at 1,261 mature individuals (95% CI=1,205-1,317) following surveys conducted from 2011-2012 (VanderWerf et al. 2013), consisting of about 477 breeding pairs and 307 single males. This total includes 592 males (95% CI= 554-630) and 369 females in the Ko'olau Mountains and 192 males and 84 females in the Wai' anae Mountains (VanderWerf et al. 2011a, 2013). The genetically effective population size may be even lower because of the fragmented distribution (VanderWerf et al. 2001, 2013). 
The largest subpopulations are in the central (523 mature individuals) and southeastern Ko’olau (403 mature individuals) Mountains, with smaller subpopulations in ‘Ekahanui (100 mature individuals), Schofield Barracks West Range (104 mature individuals), Palehua (41 mature individuals), Waikane and Kahana Valleys (24 mature individuals), and several tiny fragments containing 1-5 mature individuals each (VanderWerf 2012a).

Trend justification: Surveys conducted in the 1990s produced evidence that the species had declined by more than 75% since 1975 and by approximately 96% since the arrival of humans (VanderWerf et al. 2001). The species has continued to decline over much of its range, particularly in the Wai`anae mountains, where only 300 birds were found in 2006-2010 (VanderWerf et al. 2011a), and overall has declined in abundance by about 50% since the 1990s, when the population was estimated to be about 1,974 birds (VanderWerf et al. 2001). Numbers have been shown to remain stable or increase in areas where rats are controlled (VanderWerf et al. 2013). The overall trend of the species in the O?ahu Army Natural Resources Program (OANRP) recovery areas (Schofield Barracks Military Reservation, ?kahanui Gulch in Honouliuli Forest Reserve, Palehua and Moanalua Valley) has remained somewhat stable between 2013-2018, likely due to effective predator control in these areas (USFWS 2019). In 2017 the number of ‘elepaios in the area where rats had been controlled in Pia Valley had declined somewhat since 2007, which was the last year of rodent control (VanderWerf 2017). Between 2013 and 2018, the number of pairs appears to have declined in Wailupe Valley (USFWS 2019). Little is known on the status of O?ahu ?Elepaio outside of the OANRP recovery areas and Wailupe Valley, although populations continue to be limited by habitat loss, modification and avian disease and predation (USFWS 2019). It is likely that areas where rats are controlled serve as sources of emigrants that help to support adjacent areas where declines are ongoing due to high levels of predation (VanderWerf et al. 2013). Given that stability of populations is heavily reliant on rodent control and that rats are not sufficiently controlled throughout the range (USFWS 2019), the population is inferred to be declining overall.

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

Country/Territory	IBA Name
USA	Oahu Uplands

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Forest	Subtropical/Tropical Dry	major	resident
Forest	Subtropical/Tropical Moist Lowland	major	resident
Forest	Subtropical/Tropical Moist Montane	major	resident
Altitude	200 - 800 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
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Ecosystem degradation, Ecosystem conversion
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Felis catus	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Herpestes auropunctatus	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Plasmodium relictum	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Rattus rattus	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Reduced reproductive success, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Sus scrofa	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Indirect ecosystem effects, Ecosystem degradation
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Unspecified species	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Negligible declines		Low Impact: 5
		Stresses Ecosystem degradation
Invasive and other problematic species, genes & diseases	Viral/prion-induced diseases - Avipoxvirus	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Reduced reproductive success, Species mortality
Natural system modifications	Fire & fire suppression - Increase in fire frequency/intensity	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation
Residential & commercial development	Housing & urban areas	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Ecosystem degradation, Ecosystem conversion

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Recommended citation
BirdLife International (2024) Species factsheet: Oahu Elepaio Chasiempis ibidis. Downloaded from https://datazone.birdlife.org/species/factsheet/oahu-elepaio-chasiempis-ibidis on 22/12/2024.
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 22/12/2024.