• 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
-	-	-

Red List history

Year	Category	Criteria
2021	Least Concern
2018	Least Concern
2016	Near Threatened	A2bc+3bc+4bc
2012	Near Threatened	A2bc+3bc+4bc
2008	Near Threatened	A2b,c; A3b,c; A4b,c
2004	Near Threatened
2000	Lower Risk/Least Concern
1994	Lower Risk/Least Concern
1988	Lower Risk/Least Concern

Migratory status	full migrant	Forest dependency	low
Land-mass type	continent	Average mass	8 g

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	4,930,000 km2	medium
Extent of Occurrence (non-breeding)	1,380,000 km2	medium
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	5700000 mature individuals	medium	inferred	2019
Population trend	increasing	medium	inferred	1998-2008
Rate of change over the past 10 years/3 generations (longer of the two periods)	11%	-	-	-
Generation length	2.34 years	-	-	-

Population justification: The global population is inferred to number 5,700,000 mature individuals (Partners in Flight 2019). The California subspecies now numbers approximately 3,000 territorial males (Kus et al. 2010).

Trend justification: The species has been increasing at an average rate of 1.1% per year between 1970 and 2017 (Partners in Flight 2019). Assuming that the increase continues at the same rate, this would equate to an increase of 12% over the past ten years. The population in North America is increasing rapidly at a rate of 29% over the past ten years (Pardieck et al. 2018).

Country/Territory	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
El Salvador	extant	native			yes
Guatemala	extant	native			yes	yes
Honduras	extant	native			yes
Mexico	extant	native	yes	yes	yes	yes
Nicaragua	extant	native			yes
USA	extant	native		yes

Country/Territory	IBA Name
Mexico	Nacimiento Río Sabinas-Sureste de la Sierra de Santa Rosa
Mexico	Presa Cajón de Peñas
Mexico	Presa el Tulillo
Mexico	Presa Venustiano Carranza
Mexico	Sierra Maderas del Carmen
Mexico	Vallecitos de Zaragoza
USA	Anza-Borrego Riparian
USA	Bill Williams River National Wildlife Refuge
USA	Camp Pendleton
USA	Fort Chaffee
USA	Lower San Pedro River
USA	Lynnville-Squaw Creek Mine Complex
USA	San Diego NWR Otay-Sweetwater Unit
USA	San Luis Rey River
USA	San Pasqual Valley - Lake Hodges
USA	San Pedro Riparian National Conservation Area
USA	Santa Ana River Valley
USA	Santa Clara River Valley

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Forest	Subtropical/Tropical Moist Lowland	suitable	non-breeding
Forest	Temperate	major	breeding
Shrubland	Subtropical/Tropical Dry	major	non-breeding
Shrubland	Subtropical/Tropical Dry	major	breeding
Shrubland	Subtropical/Tropical High Altitude	suitable	non-breeding
Shrubland	Subtropical/Tropical High Altitude	suitable	breeding
Shrubland	Subtropical/Tropical Moist	suitable	non-breeding
Shrubland	Subtropical/Tropical Moist	suitable	breeding
Shrubland	Temperate	suitable	breeding
Altitude	0 - 2000 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		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture	Livestock farming & ranching - Scale Unknown/Unrecorded	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Unknown		Unknown
		Stresses Ecosystem degradation, Ecosystem conversion
Biological resource use	Logging & wood harvesting - Unintentional effects: (subsistence/small scale) [harvest]	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Unknown		Unknown
		Stresses Ecosystem degradation
Invasive and other problematic species, genes & diseases	Problematic native species/diseases	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Slow, Significant Declines		Medium Impact: 6
		Stresses Species mortality
Natural system modifications	Dams & water management/use - Dams (size unknown)	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Unknown		Unknown
		Stresses Ecosystem degradation, Ecosystem conversion
Pollution	Agricultural & forestry effluents - Type Unknown/Unrecorded	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Unknown		Unknown
		Stresses Ecosystem degradation
Residential & commercial development	Housing & urban areas	Timing		Scope		Severity		Impact
		Ongoing		Unknown		Unknown		Unknown
		Stresses Ecosystem degradation, Ecosystem conversion

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Recommended citation
BirdLife International (2024) Species factsheet: Bell's Vireo Vireo bellii. Downloaded from https://datazone.birdlife.org/species/factsheet/bells-vireo-vireo-bellii on 15/12/2024.
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 15/12/2024.