EN
Worthen's Sparrow Spizella wortheni



Taxonomy

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.

IUCN Red list criteria met and history
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
Species attributes

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

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 13,900 medium
Number of locations -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals 250-999 good estimated 2016
Population trend Decreasing poor suspected -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) 1-9 - - -
Decline (10 years/3 generation past and future) 1-9 - - -
Number of subpopulations - - -
Percentage in largest subpopulation 100 - - -
Generation length (yrs) 3.8 - - -

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 distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
Mexico N Extant Yes
USA N Extinct Yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Mexico El Manantial
Mexico Pradera de Tokio
Mexico Sierra Catorce
Mexico Sierra de Santa Rosa
Mexico Sierra de Arteaga

Habitats & altitude
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  

Threats & impact
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

Recommended citation
BirdLife International (2022) Species factsheet: Spizella wortheni. Downloaded from http://www.birdlife.org on 27/06/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 27/06/2022.