• 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(ii)	C2a(i,ii); D1+2

Red List history

Year	Category	Criteria
2017	Endangered	C2a(ii)
2016	Endangered	B1ab(i,ii,iii,v); C2a(i); D
2013	Endangered	B1ab(i,ii,iii,v); C2a(i); D
2012	Endangered	B1ab(i,ii,iii,v);C2a(i);D
2008	Endangered	B1a+b(i,ii,iii,v); C2a(i); D1
2004	Endangered
2000	Endangered
1996	Endangered
1994	Endangered
1988	Lower Risk/Least Concern

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

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	13,900 km2	medium
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	250-999 mature individuals	good	estimated	2016
Population trend	decreasing	poor	suspected	1998-2008
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	3.8 years	-	-	-
Percentage of mature individuals in largest subpopulation	100%	-	-	-

Population justification: Wintering flocks of over 100 individuals have been observed in several occasions in Nuevo León (2014-2015), Coahuila (2010-2011) and San Luis Potosí (2010-2014), with a maximum flock size of 480 Worthen’s sparrows in San Luis Potosí (2010; Ruvalcaba-Ortega et al. in prep.). Precautionarily assuming that such flocks comprise the majority or even all of the remaining population, and given the very low productivity in the species, the total population size may be only best placed in the range 250-999 mature individuals; and their winter flocking behaviour would therefore suggest the species consists of one subpopulation. Previous smaller estimations (60-100; Canales del Castillo et al. 2010) recorded in 2006, may have been due to the lack of more widespread survey efforts.

Trend justification: There are no new data on population trends; however, the species is suspected to be declining at a slow rate owing to inappropriate grazing regimes.

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

Country/Territory	IBA Name
Mexico	El Manantial
Mexico	Pradera de Tokio
Mexico	Sierra Catorce

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Grassland	Subtropical/Tropical High Altitude	major	resident
Shrubland	Subtropical/Tropical Dry	major	resident
Altitude	1200 - 2450 m	Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Annual & perennial non-timber crops - Scale Unknown/Unrecorded	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Slow, Significant Declines		Medium Impact: 7
		Stresses Ecosystem degradation, Ecosystem conversion
Agriculture & aquaculture	Annual & perennial non-timber crops - Small-holder 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 - Agro-industry grazing, ranching or farming	Timing		Scope		Severity		Impact
		Ongoing		Whole (>90%)		Slow, Significant Declines		Medium Impact: 7
		Stresses Ecosystem degradation, Ecosystem conversion
Invasive and other problematic species, genes & diseases	Problematic native species/diseases	Timing		Scope		Severity		Impact
		Ongoing		Majority (50-90%)		Unknown		Unknown
		Stresses Reduced reproductive success

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Recommended citation
BirdLife International (2024) Species factsheet: Worthen's Sparrow Spizella wortheni. Downloaded from https://datazone.birdlife.org/species/factsheet/worthens-sparrow-spizella-wortheni 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.