The Bananal Antbird (Cercomacra ferdinandi) is endemic to the Araguaia-Tocantins basin, Brazil, occurring in Pará and Maranhão, through Tocantins and south to Mato Grosso and south to Goiás (Olmos et al. 2006, Vasconcelos 2008, Kirwan et al. 2015, Crozariol et al. 2016, WikiAves 2018). It occurs along the banks and tributaries of the Araguaia river from the Ilha do Bananal to the confluence with the river Tocantins, and along the banks and tributaries of the Tocantins river south to Palmeirante (Olmos et al. 2006, Vasconcelos 2008). It inhabits dense vine tangles in riparian thickets and forest undergrowth near water (frequently in seasonally flooded areas and oxbow lakes).
The primary threat to the species is thought to be the development of hydroelectricity. The Estreito Hydro-Power Complex was recently constructed in the Tocantins-Araguaia river basin and within the species’s range (T. Dornas in litt. 2020), going into operation in 2011. Previously, there were plans to construct three further hydroelectrical plants within the species’s range (Marabá, Serra Quebrada and Santa Isabel) by 2025 (Brasil Choueri et al. 2017, Dornas & Pinheira 2018).
The species is currently listed as Vulnerable because it was suspected to have suffered a rapid population decline as a result of the construction of hydroelectric plants, and because the declines were projected to continue owing to further dam construction. However, the plans for the three further dams within the species’s range are currently on hold and they are not expected to be constructed within the next 5-10 years (T. Dornas in litt. 2020). Hence, we are undertaking a review of the species’s Red List Category. Our current information on the species’s conservation status will now be compared to all Red List Criteria.
Criterion A – This species is estimated to have a generation length of 2.68 years (Bird et al. 2020)*. Hence reductions are here assessed over a period of ten years.
The Estreito Hydro-Power Complex was recently constructed in the Tocantins-Araguaia river basin and within the range of the Bananal Antbird (T. Dornas in litt. 2020), going into operation in 2011. Remote-sensed data on tree cover indicated a loss of 15% of tree cover with 50% canopy cover within the range over 10 years from 2009-2018 (Global Forest Watch 2020). The rate of deforestation in the range was particularly high in 2016 (Global Forest Watch 2020), and the rate of deforestation in the legal Amazon increased by around a third from 2018-2019 (INPE 2019). Furthermore, an analysis of the impact of disturbance on forest species in Pará found that in private lands or sustainable-use reserves, the impact of disturbance on biodiversity was equivalent to that of an additional 51% loss of forest (Barlow et al. 2016). However, this species is known to be tolerant of disturbed habitats (T. Dornas in litt. 2020) and it occurs in flooded forest, which is likely to be subject to lower levels of deforestation than terra firma forest. Overall, a population reduction of 10-29% is suspected to have occurred over the last ten years. This could qualify the species as Least Concern or Near Threatened under Criterion A2c, depending the most likely magnitude of population reductions and the level of uncertainty.
Although there were plans to construct three further hydroelectrical plants within the species’s range by 2025 (Brasil Choueri et al. 2017), the plans are currently on hold and the plants are not expected to be constructed within the next 5-10 years (T. Dornas in litt. 2020). If the average 2016-2018 deforestation rate were to continue over the next ten years, this would equate to a loss of 27% of forest within the species’s range. Considering the increase in deforestation seen in the legal Amazon in 2019, a loss of >30% of tree cover within the species’s range may occur over the next decade. Thus, assuming the population size is proportional to forest area, and adding the potential impact of disturbance, the population size could be suspected to undergo a reduction of up to 52% over three generations. However, given that the species is tolerant of some habitat disturbance and occurs in flooded forest, the reduction over the next ten years is suspected to be lower than this, and is here placed in the band 10-49%. This also likely applied over ten years from c. 2016. Thus, the species may qualify for assessment as Least Concern, Near Threatened or Vulnerable under Criteria A3c+4c, depending the most likely magnitude of population reduction over the next decade, and the level of uncertainty.
Criterion B – The Extent of Occurrence (EOO) is inferred to be 209,000 km2, based on the area of a minimum convex polygon around the species’s mapped range (revised in 2020 and not yet visible on the Data Zone). This does not approach the threshold for listing the species as threatened under Criterion B1. The Area of Occupancy (AOO) has not been quantified, but is unlikely to approach the thresholds for listing as threatened under Criterion B2. Bananal Antbird is therefore assessed as Least Concern under Criterion B.
Criterion C – A study of ten territories at RPPN Canguçu in Tocantins found an average territory density of 0.31 per ha (31 territories/km2), ranging from 0.14 to 0.64 territories/ha (Crozariol 2011). Based on these densities, a population of 220,000 pairs was estimated for Cantão State Park (Crozariol 2011). Studies at the Murici and Preto rivers, tributaries of the Araguaia, in the north of Tocantins, detected at least 22 individuals in a 1 km transect in floodplain vegetation (Dornas & Pinheiro 2018).
Based on knowledge of the species’s distribution and population densities, the population size has been estimated at 15,000 – 20,000 mature individuals (T. Dornas in litt. 2020). Based on the recorded population densities, the area of tree cover with 50% canopy cover within within the mapped range (estimated at 46,600km2; Global Forest Watch 2020), and assuming 10-25% of the forest is occupied, the population is estimated at 195,720 – 489,300 individuals, roughly equating to 130,480 – 326,200 mature individuals. Based on these estimates, the population size is here placed in the band 15,000 – 350,000 mature individuals. This may approach the threshold for listing the species as Near Threatened under Criterion C, or qualify it as Least Concern.
A continuing decline in population size may be inferred from remote-sensed data on forest loss within the species’s range (Global Forest Watch 2020). We have no data from which to infer or estimate a rate of population decline, so the species cannot be assessed under Criterion C1. There are no large gaps between areas with records and the species is considered to have a relatively high dispersal ability (Borges et al. 2019), so it is assumed to have one subpopulation. This would meet condition C2a(ii). The species is not composed of subpopulations of less than 1,000 mature individuals and it is not undergoing extreme fluctuations, so conditions C2a(i) and C2b are not met.
Bananal Antbird is undergoing a continuing decline and is thought to have a single subpopulation. If the lower end of the range of population size estimates (i.e. 15,000 mature individuals) is accepted, the species could qualify for Near Threatened, approaching the thresholds for listing as threatened under Criterion C2a(ii). However, given the wide range of population size estimates, and the previous population estimate of 220,000 pairs in one protected area alone, it is unlikely that the population size is as small as 15,000 mature individuals. The species is therefore assessed as Least Concern under Criterion C.
Criterion D – Based on the population estimates described above, the population size does not meet or approach the threshold for Vulnerable under Criterion D. The species is therefore assessed as Least Concern under this criterion.
Criterion E – To the best of our knowledge no quantitative assessment of the probability of extinction has been conducted for this species, and so it cannot be assessed against this criterion.
The species could qualify for any category from Least Concern to Vulnerable, depending on the suspected population reduction over the next ten years. To allow us to achieve a clearer assessment of the species’s status, information is requested on the species’s projected population reduction of the Bananal Antbird over the next ten years. In particular:
- Is the species’s habitat likely to suffer significantly less deforestation than that seen in the surrounding region?
- How is the species likely to be affected by disturbance?
Please note that a species should only be downlisted to a lower category of threat on the IUCN Red List when current information indicates that it has not qualified for the higher category for at least five years. Therefore, if there is evidence to suggest that, at any time over the past five years, the species’s population reduction had been greater than 30% over the previous decade (i.e. across 10-year periods from 2005-2015 onwards), the species should be retained as Vulnerable under Criterion A2.
Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of the species’s Red List status. Therefore, please make sure your comments are about the proposed listing. By submitting a comment, you confirm that you agree to the Comment Policy.
*Bird generation lengths are estimated using the methodology of Bird et al. (2020), as applied to parameter values updated for use in each IUCN Red List for birds reassessment cycle. Values used for the current assessment are available on request. We encourage people to contact us with additional or improved values for the following parameters; adult survival (true survival accounting for dispersal derived from an apparently stable population); mean age at first breeding; and maximum longevity (i.e. the biological maximum, hence values from captive individuals are acceptable).
An information booklet on the Red List Categories and Criteria can be downloaded here and the Red List Criteria Summary Sheet can be downloaded here. Detailed guidance on IUCN Red List terms and definitions and the application of the Red List Categories and Criteria can be downloaded here.
Bird, J. P., Martin, R., Akçakaya, H. R., Gilroy, J., Burfield, I. J., Garnett, S. G., Symes, A., Taylor, J., Şekercioğlu, Ç. H. and Butchart, S. H. M. 2020. Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology online first view.
Borges, F. J. A., Ribeiro, B. R., Lopes, L. E., & Loyola, R. 2019. Bird vulnerability to climate and land use changes in the Brazilian Cerrado. Biological Conservation 236: 347-355.
Brasil Choueri, R., Azevedo, and R., Anderson, J. 2017. Biodiversidade e impacto de grandes empreendimentos hidrelétricos na bacia Tocantins-Araguaia: uma análise sistêmica. Sociedade & Natureza 29(3): 443-457.
Crozariol, M. A. 2011. Territorialidade e reprodução do Chororó-do-araguaia, Cercomacra ferdinandi Snethlage, 1928 (passeriformes: thamnophilidae) em uma área ecotonal no estado de Tocantins. Universidade Federal do Tocantins.
Crozariol, M. A. 2016. Ampliação austral da distribuição do chororó-de-goiás, Cercomacra ferdinandi, com os primeiros registros da espécie no estado de Goiás, Brasil. Atualidades Ornitológicas 190: 25-26.
Dornas, T. and Pinheiro, R. T. 2018. Cercomacra ferdinandi Snethlage, 1928. In: ICMBio/MMA (ed.), Livro Vermelho da Fauna Brasileira Ameaçada de Extinção: Volume III – Aves, pp. 355-358. Brasília, DF.
Global Forest Watch. 2020. Interactive Forest Change Mapping Tool. Available at: http://www.globalforestwatch.org/.
INPE. 2019. A estimativa da taxa de desmatamento por corte raso para a Amazônia Legal em 2019 é de 9.762 km². São José dos Campos-SP Available at: http://www.inpe.br/noticias/noticia.php?Cod_Noticia=5294. (Accessed: 25 March 2020).
Kirwan, G. M., Whittaker, A. & Zimmer, K. J. 2015. Interesting bird records from the Araguaia River Valley, central Brazil, with comments on conservation, distribution and taxonomy. Bull. Brit. Orn. Club 135: 21-60.
Olmos, F., Silva e Silva, R., Pacheco, J. F. 2006. The range of Bananal antbird Cercomacra ferdinandi. Cotinga 25: 21-23.
Vasconcelos, M. F. de; de Souza Werneck, M. 2008. Northern record for Bananal Antbird Cercomacra ferdinandi. Cotinga: 177-178.
WikiAves. 2018. Chororó-de-goiás. Available at: https://www.wikiaves.com.br/wiki/chororo-de-goias?s=%2Aferdinandi%2A. (Accessed: 9 April 2020).