EN
Yellow-shouldered Blackbird Agelaius xanthomus



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
- B2ab(iii,v) B1ab(iii,v)+2ab(iii,v); C1; D1

Red List history
Year Category Criteria
2020 Endangered B2ab(iii,v)
2016 Endangered B2ab(iii,v)
2012 Endangered B1ab(i,ii,iii,v)
2008 Endangered B1a+b(i,ii,iii)
2004 Endangered
2000 Endangered
1996 Endangered
1994 Endangered
1988 Threatened
Species attributes

Migratory status not a migrant Forest dependency Low
Land mass type Average mass 38 g
Distribution

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 9,000 medium
Extent of Occurrence breeding/resident (km2) 260
Number of locations 2-5 -
Severely Fragmented -
Population and trend
Value Data quality Derivation Year of estimate
No. of mature individuals 250-999 poor estimated 1998
Population trend Decreasing poor estimated -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) 11.4 - - -
Decline (10 years/3 generation past and future) 11.4 - - -
Number of subpopulations 2-100 - - -
Percentage in largest subpopulation 1-89 - - -

Population justification: In early 1998, the total population was estimated at 1,250 individuals (Jaramillo and Burke 1999), which equates to 833 mature individuals, hence it was placed in the band 250-999 mature individuals to reflect the uncertainty and fluctuations seen in population surveys. Whilst post-breeding population estimates have been carried out for individual subpopulations in the years since, inconsistencies in the timing of surveys, some subpopulations remaining largely unsurveyed and strong interannual fluctuations within subpopulations makes the generation of a new, total population estimate difficult. The latest estimates suggest approximately 400-1,000 individuals in the southwest population, ~150 individuals on Mona Island, 80-120 individuals in Salinas and at least 8-10 individuals in the eastern population (USFWS 2011, 2018, 2019, unpubl. data). This totals ~638-1,280 individuals, which equates to ~425-853 mature individuals. This estimate falls within the same range, 250-999 mature individuals, hence the population estimate is retained in this band.

Trend justification: The total number of individuals is tentatively thought to have exhibited a slight increase in the past 25 years (J. Martínez in litt. 2020). The population in southwestern Puerto Rico was considered improving in 2011 (USFWS 2011). However, the population then declined by more than 50%, leaving fewer than 400 individuals by August 2012 (Miller et al. 2016). Subsequently, the population was estimated through the post-breeding survey in 2012 at more than 650 individuals (Miller et al. 2016). This population was then recorded at just 424 individuals the post-breeding period of November 2015, before rapidly increasing to 1056 individuals in the post-breeding season in September 2016 (USFWS 2018); it is thought that populations in the southwest fluctuate strongly and typically range annually between 400-1,000 individuals (USWFS 2018, 2019, J. Martínez in litt. 2020). The status of the eastern and southern populations is largely unknown, but overall the population is considered to be stable (R. Miranda-Medina in litt. 2012). In Salinas (southeastern Puerto Rico), 113 individuals were observed during the post-breeding census of 2005, a slight increase from 2004 (97 individuals), however, just 82 individuals were identified in the post-breeding period of November 2012 (USFWS 2011, 2012). Overall, there is no clear reduction over the past ten years and it would appear that the population fluctuates considerably year-on-year, possibly as a result of low, inconsistent juvenile recruitment (USFWS, I. Liu in litt. 2020). In 2012, a population and habitat viability analysis (PHVA) modelled the outcomes of different management strategies and found that, even with incumbent management practices, the Yellow-shouldered Blackbird is currently experiencing a negative growth rate with a 31 % chance of extinction in the next 50 years (Medina-Miranda et al. 2013). Therefore, the population is considered to be likely to decline slowly in the future.


Country/territory distribution
Country/Territory Occurrence status Presence Resident Breeding Non-breeding Passage
Puerto Rico (to USA) N Extant Yes

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name
Puerto Rico (to USA) Sierra Bermeja and Laguna Cartagena
Puerto Rico (to USA) Reserva Natural De La Parguera
Puerto Rico (to USA) Bosque Estatal de Boquerón inlcuyendo Punta Melones y Pitahaya
Puerto Rico (to USA) Jobos Bay
Puerto Rico (to USA) Ceiba and Naguabo
Puerto Rico (to USA) Karso del Sur
Puerto Rico (to USA) Guaniquilla and Boquerón
Puerto Rico (to USA) Mona and Monito
Puerto Rico (to USA) Suroeste
Puerto Rico (to USA) Caño Tiburones
Puerto Rico (to USA) Cienaga Las Cucharillas
Puerto Rico (to USA) Acantilados del Noroeste
Puerto Rico (to USA) Salinas de Punta Cucharas
Puerto Rico (to USA) Humacao

Habitats & altitude
Habitat (level 1) Habitat (level 2) Importance Occurrence
Artificial/Terrestrial Arable Land suitable non-breeding
Artificial/Terrestrial Pastureland suitable non-breeding
Forest Subtropical/Tropical Mangrove Vegetation Above High Tide Level suitable breeding
Shrubland Subtropical/Tropical Dry suitable breeding
Altitude   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 Minority (<50%) Slow, Significant Declines Low Impact: 5
Stresses
Ecosystem degradation, Ecosystem conversion
Climate change & severe weather Storms & flooding Timing Scope Severity Impact
Ongoing Majority (50-90%) Unknown Unknown
Stresses
Indirect ecosystem effects, Ecosystem degradation, Reduced reproductive success
Human intrusions & disturbance Recreational activities Timing Scope Severity Impact
Ongoing Unknown Unknown Unknown
Stresses
Species disturbance
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Herpestes auropunctatus Timing Scope Severity Impact
Ongoing Majority (50-90%) Rapid Declines Medium Impact: 7
Stresses
Reduced reproductive success
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Molothrus bonariensis Timing Scope Severity Impact
Ongoing Minority (<50%) Unknown Unknown
Stresses
Reduced reproductive success
Invasive and other problematic species, genes & diseases Invasive non-native/alien species/diseases - Rattus rattus Timing Scope Severity Impact
Ongoing Majority (50-90%) Rapid Declines Medium Impact: 7
Stresses
Reduced reproductive success
Invasive and other problematic species, genes & diseases Problematic native species/diseases - Margarops fuscatus Timing Scope Severity Impact
Ongoing Majority (50-90%) Negligible declines Low Impact: 5
Stresses
Species disturbance, Reduced reproductive success
Invasive and other problematic species, genes & diseases Problematic native species/diseases - Progne dominicensis Timing Scope Severity Impact
Ongoing Majority (50-90%) Negligible declines Low Impact: 5
Stresses
Species disturbance, Reduced reproductive success
Invasive and other problematic species, genes & diseases Problematic native species/diseases - Unspecified species Timing Scope Severity Impact
Ongoing Unknown Unknown Unknown
Stresses
Reduced reproductive success
Other options Other threat Timing Scope Severity Impact
Ongoing Whole (>90%) Unknown Unknown
Stresses
Inbreeding, Other
Residential & commercial development Housing & urban areas Timing Scope Severity Impact
Ongoing Unknown Unknown Unknown
Stresses
Ecosystem conversion
Residential & commercial development Tourism & recreation areas Timing Scope Severity Impact
Ongoing Unknown Unknown Unknown
Stresses
Ecosystem conversion

Utilisation
Purpose Primary form used Life stage used Source Scale Level Timing
Pets/display animals, horticulture - - International Non-trivial Recent

Recommended citation
BirdLife International (2022) Species factsheet: Agelaius xanthomus. Downloaded from http://www.birdlife.org on 11/08/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 11/08/2022.