Marsh Antwren Formicivora paludicola


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.

IUCN Red list criteria met and history
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)
Species attributes

Migratory status not a migrant Forest dependency Does not normally occur in forest
Land mass type Average mass -
Extent of occurrence (EOO)

Estimate Data quality
Extent of Occurrence breeding/resident (km2) 1,500
Extent of Occurrence breeding/resident (km2) 10
Number of locations 11-100 -
Fragmentation -
Population and trend
Estimate Data quality Derivation Year of estimate
No. of mature individuals 150-700 good estimated 2014
Population trend Unknown -
Decline (3 years/1 generation past) - - -
Decline (5 years/1 generation past) - - -
Decline (10 years/1 generation past) - - -
Decline (10 years/3 generation future) - - -
Decline (10 years/3 generation past and future) - - -
Number of subpopulations 3 - - -
Largest subpopulations 1-89 - - -
Generation length (yrs) 4.8 - - -

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

Important Bird and Biodiversity Areas (IBA)
Country/Territory IBA Name

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

Threats & impact
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
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
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
Ecosystem degradation
Residential & commercial development Commercial & industrial areas Timing Scope Severity Impact
Future Majority (50-90%) Very Rapid Declines Medium Impact: 6
Species disturbance, Ecosystem conversion, Species mortality

Recommended citation
BirdLife International (2020) Species factsheet: Formicivora paludicola. Downloaded from on 29/09/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from on 29/09/2020.