• 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.
SACC. 2005 and updates. A classification of the bird species of South America. Available at: https://www.museum.lsu.edu/~Remsen/SACCBaseline.htm.

Red List criteria met

Critically Endangered	Endangered	Vulnerable
-	-	-

Red List history

Year	Category	Criteria
2022	Near Threatened	C2a(i)
2016	Vulnerable	B1ab(i,ii,iii,v);C2a(i)
2013	Vulnerable	B1ab(i,ii,iii,v);C2a(i)
2012	Vulnerable	B1ab(i,ii,iii,v);C2a(i)
2008	Vulnerable	B1a+b(i,ii,iii,v); C2a(i)
2004	Vulnerable
2000	Vulnerable
1996	Vulnerable
1994	Vulnerable
1988	Lower Risk/Least Concern

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

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	258,000 km2	medium
Area of Occupancy (breeding/resident)	17,000 km2
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	7300-8000 mature individuals	poor	estimated	2022
Population trend	decreasing	poor	suspected	2016-2026
Rate of change over the past 10 years/3 generations (longer of the two periods)	1-9%	-	-	-
Rate of change over the future 10 years/3 generations (longer of the two periods)	1-9%	-	-	-
Rate of change over the past & future 10 years/3 generations (longer of the two periods)	1-9%	-	-	-
Generation length	3.26 years	-	-	-
Number of subpopulations	11-100	-	-	-
Percentage of mature individuals in largest subpopulation	1-89%	-	-	-

Population justification: Field surveys in the Tapichalaca Reserve, Ecuador, found the species to occur at a density of 1 individual/km² (Harris et al. 2008, Renjifo et al. 2014). Assuming that this density is representative for the entire range, and further precautionarily assuming that only 50% of forested habitat within the range is occupied (i.e. 50% of 11,000-12,000 km²; Global Forest Watch 2022), the total population may number 11,000-12,000 individuals. This is roughly equivalent to 7,300-8,000 mature individuals.

Trend justification: The population trend has not been quantified directly, but it is feared that the population is declining as a consequence of habitat loss within the range. Tree cover loss within the range is currently low (<2% over ten years; Global Forest Watch 2022, using Hansen et al. [2013] data and methods disclosed therein). Even though it may also be found in tall secondary forest and along natural gaps, the species is restricted to humid forest (Zimmer and Isler 2020), and thus population declines may be aggravated by additional habitat degradation. Nevertheless, it is unlikely that declines exceed 10% over ten years.

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

Country/Territory	IBA Name
Colombia	La Planada Natural Reserve
Colombia	Munchique Natural National Park and southern extension
Colombia	Parque Nacional Natural Tatamá
Colombia	Reserva Natural Río Ñambí
Colombia	Reserva Natural Tambito
Ecuador	Cordillera de Huacamayos-San Isidro-Sierra Azul
Ecuador	Corredor Ecológico Llanganates-Sangay
Ecuador	El Ángel - Cerro Golondrinas and surrounding areas
Ecuador	Parque Nacional Sangay
Ecuador	Parque Nacional Sumaco-Napo Galeras
Ecuador	Territorio Étnico Awá y alrededores

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Forest	Subtropical/Tropical Moist Montane	major	resident
Altitude	900 - 2530 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
Agriculture & aquaculture	Annual & perennial non-timber crops - Small-holder farming	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture	Livestock farming & ranching - Agro-industry 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		Minority (<50%)		Slow, Significant Declines		Low Impact: 5
		Stresses Ecosystem degradation, Ecosystem conversion
Energy production & mining	Mining & quarrying	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Ecosystem degradation, Ecosystem conversion
Residential & commercial development	Housing & urban areas	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Ecosystem degradation, Ecosystem conversion
Transportation & service corridors	Roads & railroads	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Negligible declines		Low Impact: 4
		Stresses Ecosystem degradation, Ecosystem conversion

---

Recommended citation
BirdLife International (2024) Species factsheet: Bicolored Antvireo Dysithamnus occidentalis. Downloaded from https://datazone.birdlife.org/species/factsheet/bicolored-antvireo-dysithamnus-occidentalis on 22/11/2024.
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 22/11/2024.