• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Taxonomic note

Formicivora paludicola (del Hoyo and Collar 2016) is recognized following evidence presented in Buzzetti et al. (2013).

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)	B2ab(iii); D	B2ab(iii); D1

Red List history

Year	Category	Criteria
2018	Critically Endangered	B2ab(iii)
2016	Critically Endangered	B2ab(iii)
2012	Not Recognised
2008	Not Recognised
2004	Not Recognised
2000	Not Recognised
1994	Not Recognised
1988	Not Recognised

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

	Estimate	Data quality
Extent of Occurrence (breeding/resident)	1,500 km2
Area of Occupancy (breeding/resident)	10 km2
Number of locations	11-100	-
Severely fragmented?	yes	-

	Estimate	Data quality	Derivation	Year of estimate
Population size	150-700 mature individuals	good	estimated	2014
Population trend	unknown	-	-	-
Generation length	4.8 years	-	-	-
Number of subpopulations	3	-	-	-
Percentage of mature individuals in largest subpopulation	1-89%	-	-	-

Population justification: The population was initially estimated at between 250 and 300 individuals, but genetic analysis demonstrated an effective population size of approximately 50 birds in each of the three largest populations, estimated to represent a census size of between 220-582 individuals within approximately 60% of the total area of marsh habitat within the sites where the species has been recorded (Camargo et al. 2015). Accordingly, the population of the species can be placed with good confidence in the band 250-1,000 individuals, roughly equivalent to 166-667 mature individuals which is rounded here to 150-700 mature individuals. The genetic structure of the subpopulations has been investigated and suggests that even though the species is highly restricted in range, there is a considerable degree of genetic differentiation between the three sites holding the largest number of individuals, indicating a minimum of three subpopulations within the species (Camargo et al. 2015). This finding indicates that the species can be considered to be severely fragmented, with each subpopulation at risk of extinction with limited possibility of recolonization.

Trend justification: Two of the sites at which the species has been recorded have been lost subsequent to their discovery. 72 individuals were captured and translocated from one of these sites to 10 surrounding marshes of which seven appeared to be new sites. Therefore, despite the loss of two sites, the population trend is not suspected to be decreasing as birds have begun breeding at the new sites. The population trend is uncertain.

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

Country/Territory	IBA Name

Habitat (level 1)	Habitat (level 2)	Importance	Occurrence
Wetlands (inland)	Bogs, Marshes, Swamps, Fens, Peatlands	major	resident
Altitude		Occasional altitudinal limits

Threat (level 1)	Threat (level 2)	Impact and Stresses
Agriculture & aquaculture	Marine & freshwater aquaculture - Industrial aquaculture	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Very Rapid Declines		Medium Impact: 7
		Stresses Species disturbance, Species mortality
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Hedychium coronarium	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Rapid Declines		Medium Impact: 6
		Stresses None
Invasive and other problematic species, genes & diseases	Invasive non-native/alien species/diseases - Urochloa arrecta	Timing		Scope		Severity		Impact
		Ongoing		Minority (<50%)		Rapid Declines		Medium Impact: 6
		Stresses Ecosystem degradation
Residential & commercial development	Commercial & industrial areas	Timing		Scope		Severity		Impact
		Future		Majority (50-90%)		Very Rapid Declines		Medium Impact: 6
		Stresses Species disturbance, Ecosystem conversion, Species mortality

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Recommended citation
BirdLife International (2024) Species factsheet: Marsh Antwren Formicivora paludicola. Downloaded from https://datazone.birdlife.org/species/factsheet/marsh-antwren-formicivora-paludicola on 26/12/2024.
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 26/12/2024.