• 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
-	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

Migratory status	not a migrant	Forest dependency	low
Land-mass type		Average mass	38 g

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	9,000 km2	medium
Area of Occupancy (breeding/resident)	260 km2
Number of locations	2-5	-
Severely fragmented?	no	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	250-999 mature individuals	poor	estimated	1998
Population trend	decreasing	poor	estimated	2012-2022
Rate of change over the future 10 years/3 generations (longer of the two periods)	11.4%	-	-	-
Rate of change over the past & future 10 years/3 generations (longer of the two periods)	11.4%	-	-	-
Generation length	3.15 years	-	-	-
Number of subpopulations	2-100	-	-	-
Percentage of mature individuals 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	Presence	Origin	Resident	Breeding visitor	Non-breeding visitor	Passage migrant
Puerto Rico (to USA)	extant	native	yes

Country/Territory	IBA Name
Puerto Rico (to USA)	Ceiba and Naguabo
Puerto Rico (to USA)	Guaniquilla and Boquerón
Puerto Rico (to USA)	Jobos Bay
Puerto Rico (to USA)	Mona and Monito
Puerto Rico (to USA)	Sierra Bermeja and Laguna Cartagena
Puerto Rico (to USA)	Suroeste

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

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

Purpose	Scale
Pets/display animals, horticulture	international

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Recommended citation
BirdLife International (2024) Species factsheet: Yellow-shouldered Blackbird Agelaius xanthomus. Downloaded from https://datazone.birdlife.org/species/factsheet/yellow-shouldered-blackbird-agelaius-xanthomus on 23/11/2024.
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 23/11/2024.