Archived 2016 topics: The newly described taxon Formicivora paludicola (Marsh Antwren) is to be recognised as a species by BirdLife: list as Critically Endangered?

This is part of a consultation on the Red List implications of extensive changes to BirdLife’s taxonomy for passerines

Lynx Edicions and BirdLife International will soon publish the second volume of the HBW-BirdLife Illustrated Checklist of the Birds of the World, building off the Handbook of the Birds of the World series, and BirdLife’s annually updated taxonomic checklist.

The new Checklist will be based on the application of criteria for recognising species limits described by Tobias et al. (2010). Full details of the specific scores and the basis of these for each new taxonomic revision will be provided in the Checklist.

Following publication, an open and transparent mechanism will be established to allow people to comment on the taxonomic revisions or suggest new ones, and provide new information of relevance in order to inform regular updates. We are also actively seeking input via a discussion topic here regarding some potential taxonomic revisions that currently lack sufficient information.

The new Checklist will form the taxonomic basis of BirdLife’s assessments of the status of the world’s birds for the IUCN Red List. The taxonomic changes that will appear in volume 2 of the checklist (for passerines) will begin to be incorporated into the 2016 Red List update, with the remainder to be incorporated into subsequent Red List updates.

Preliminary Red List assessments have been carried out for the newly split or lumped taxa. We are now requesting comments and feedback on these preliminary assessments.

The newly described taxon Formicivora paludicola is to be recognised as a species by BirdLife following application of the Tobias et al. (2010) criteria, which support its distinctiveness from congeners.

F. paludicola was discovered only in October 2004 and is known from a very restricted area in the headwaters of the Tietê and Paraíba do Sul river basins, Sao Paulo state, Brazil (Buzzetti et al. 2013, Kirwan 2016). The Extent of Occurrence has been estimated at 1,490 km2. 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 that 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.

Following the discovery of F. paludicola, exhaustive searches at more than 50 sites revealed its presence in a total of 15 small marshes, all less than 45 ha (Buzzetti et al. 2013). Two of these sites have subsequently been lost, one to the construction of a dam from where 72 individuals were captured and translocated to 10 surrounding marshes, 7 of which appear to be sites that previously did not hold the species (Buzzetti et al. 2013, Camargo et al. 2015). Subsequently these translocated birds have persisted and been reported to have successfully bred (Buzzetti et al. 2013). The small size and discrete nature of these sites indicate that it is safe to assume that the area of occupancy for the species falls below 10 km2.

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 concerning finding indicates that the species can be considered to be severely fragmented, with each subpopulation at risk of extinction with limited possibility of recolonization.

The habitat of the species, small bulrush and cattail marshes, is under threat from sand mining activity and other developments such as for housing or fish farming. Additionally the invasion of the marsh by the introduced grass Urochloa arrecta appears to render the marshes unsuitable for the species, and is a considerable threat (Buzzetti et al. 2013).

On the basis that the area of occupancy of the species is less than 10km2, the population is severely fragmented and there is a continuing decline in the area, extent and/or quality of habitat, the species qualifies for listing as Critically Endangered under Criterion B2ab(iii).

Comments are invited on these proposed categories and further information would be welcomed.



Buzzetti, D.R.C., Belmonte-Lopes, R., Reinert, B.L., Silveira, L.F. and Bornschein, M.R. (2013) A new species of Formicivora Swainson, 1824 (Thamnophilidae) from the state of São Paulo, Brazil. Revista Brasileira de Ornitologia 21(4): 269–291.

Camargo, C., Gibbs, H.L., Costa, M.C., Del-Rio, G., Silveira, L.F., Wasko, A.P. & Francisco, M.R. (2015) Marshes as “mountain tops”: genetic analyses of the Critically Endangered São Paulo Marsh Antwren (Aves: Thamnophilidae). PLoS ONE 10(10): e0140145.

IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. Gland, Switzerland and Cambridge, UK: IUCN Species Survival Commission.

IUCN. 2012. Guidelines for Application of IUCN Red List Criteria at Regional and National Levels: Version 4.0. Gland, Switzerland and Cambridge, UK: IUCN.

Kirwan, G.M. (2016). Marsh Antwren (Formicivora paludicola). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from on 16 September 2016).

Tobias, J. A., Seddon, N., Spottiswoode, C. N., Pilgrim, J. D., Fishpool, L. D. C. and Collar, N. J. 2010. Quantitative criteria for species delimitation. Ibis 152: 724–746.

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2 Responses to Archived 2016 topics: The newly described taxon Formicivora paludicola (Marsh Antwren) is to be recognised as a species by BirdLife: list as Critically Endangered?

  1. Daniel Lebbin says:

    New information off NEOORN, that supports listing as Critically Endangered:
    The Wilson Journal of Ornithology, 128: 2 (June 2016)
    Remarks on the Natural History of São Paulo Marsh Antwren (Formicivora paludicola)
    Glaucia Del-Rio and Luís Fábio Silveira
    The São Paulo Marsh Antwren (Formicivora paludicola) is a recently discovered species in the family Thamnophilidae that inhabits marshes in the vicinity of the São Paulo metropolitan region, which is the most populous area of South America and within the Brazilian Southeastern Atlantic Forest. This species should be considered “Critically Endangered” following IUCN criteria, as it has a total area of occupancy of only 1.42 km2, a sparse and fragmented distribution, low dispersal capacity, and has lost ~300 km2 of habitat in the last 200 years. F. paludicola was discovered on the verge of extinction, and virtually nothing is known about its natural history, breeding biology, and life history, hence compromising any conservation effort. By capturing and banding individuals from the three largest populations of São Paulo Marsh Antwrens, we provide the first assessment of the breeding period and molt cycles of F. paludicola. Our observations indicate breeding season is from October to February, and the species follows the Complex Basic molt strategy, with a partial pre-formative molt. F. paludicola also shows morphological sexual dimorphism, with males slightly larger than females.

  2. James Westrip (BirdLife) says:

    Based on available information, our preliminary proposal for the 2016 Red List would be to adopt the proposed classifications outlined in the initial forum discussion.

    There is now a period for further comments until the final deadline of 28 October, after which the recommended categorisations will be put forward to IUCN.

    Please note that we will then only post final recommended categorisations on forum discussions where these differ from those in the initial proposal.

    The final 2016 Red List categories will be published on the BirdLife and IUCN websites in early December, following further checking of information relevant to the assessments by both BirdLife and IUCN.

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