• 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
D	D	D1

Red List history

Year	Category	Criteria
2021	Critically Endangered	D
2016	Critically Endangered	D
2013	Critically Endangered	D
2012	Critically Endangered	D
2010	Critically Endangered	D1
2009	Critically Endangered	D1
2008	Critically Endangered
2004	Critically Endangered
2000	Critically Endangered
1996	Vulnerable
1994	Vulnerable
1988	Threatened

Migratory status	unknown	Forest dependency	unknown
Land-mass type	shelf island	Average mass	-

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	6,600 km2	medium
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	1-49 mature individuals	poor	estimated	2000
Population trend	unknown	-	-	-
Generation length	3.3 years	-	-	-
Number of subpopulations	1	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: The population is assumed to be tiny (fewer than 50 individuals and mature individuals) based on a lack of records, despite searches, since two specimens were collected in 1917-1918.

Trend justification: Population trends are unknown and are thus not quantified.

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

Country/Territory	IBA Name
Indonesia	Gunung Leuser

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Forest	Subtropical/Tropical Moist Lowland	possible	resident
Altitude	150 - 200 m	Occasional altitudinal limits	(min) 0 m

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Annual & perennial non-timber crops - Agro-industry farming	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture	Livestock farming & ranching - Small-holder grazing, ranching or farming	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Biological resource use	Logging & wood harvesting - Unintentional effects: (large scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Rapid Declines		Medium Impact: 7
		Stresses Ecosystem conversion
Biological resource use	Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Rapid Declines		Medium Impact: 7
		Stresses Ecosystem degradation

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Recommended citation
BirdLife International (2024) Species factsheet: Rück's Blue Flycatcher Cyornis ruckii. Downloaded from https://datazone.birdlife.org/species/factsheet/rucks-blue-flycatcher-cyornis-ruckii on 23/12/2024.
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 23/12/2024.