The Forbes’s Blackbird (Anumara forbesi) is known from widely scattered sites in Brazil, where it occurs in Pernambuco and Alagoas in the northeast, and over 1,400 km to the south in Minas Gerais, east Brazil. It inhabits forests, forest edge, adjacent marshy areas and river edges and sugarcane and mango plantations (Fraga & Sharpe 2016).
Widespread habitat destruction, particularly in north-east Brazil, through conversion to agriculture, has caused considerable habitat loss and degradation, and even reduced forest-edge areas. However, the species might be able to withstand forest conversion to plantations to some degree. Other potential threats are trapping and nest parasitism by Molothrus species.
The species is currently listed as Endangered under Criterion B2. However, the species’s AOO has not been quantified so the species requires reassessment. Our current information on the species’s conservation status will now be compared to all Red List Criteria.
Criterion A – The area of forest with at least 30% canopy cover within the species’s mapped range declined by 12% over a period of three generations (13 years; Bird et al. 2020)* from 2005-2018 (Global Forest Watch 2020). However, the species is known to inhabit forest edges as well as sugar cane and mango plantations, and non-forest habitats, so it is not known whether the reduction in forest habitat has resulted in a similar reduction in population size. The population size is suspected to be declining, but there is insufficient information to assess a rate of decline. The species cannot be assessed under this criterion.
Criterion B – The species’s extent of occurrence (EOO) is inferred to be 691,000 km2, based on a minimum convex polygon around the mapped range. This does not approach the threshold for listing the species as threatened under Criterion B1. The area of occurrence (AOO) has not been quantified. The species’s mapped range has a total area of 137,270 km2, and in 2010, there were 43,900 km2 of forest with at least 30% canopy cover within the area of the species’s mapped range (Global Forest Watch 2020). Although the species has a localised and fragmented distribution within the mapped range, we do not have evidence that the AOO is less than 2,000 km2. The species is assessed as Least Concern under Criterion B.
Criterion C – The species appears to be naturally rare and has localised subpopulations. There is little data on the population, but the total population size is thought to be 1,000-2,499 individuals (de Melo Dantas & Albano 2018), which roughly equates to 667-1,667 mature individuals, placed in the band 600-1,700 mature individuals. The species meets the initial population size threshold for listing as Endangered under Criterion C. To list the species as threatened on the Red List under Criterion C, further conditions would also need to be met.
There must also be evidence from which to infer that the species’s population size is undergoing a continuing decline. Although remote-sensed data indicates that the amount of forest within the species’s range is declining (Global Forest Watch 2020), the species is known to inhabit forest edges as well as sugar cane and mango plantations, and non-forest habitats. Therefore, although we may suspect that the population is declining, we do not consider there to be sufficient evidence from which to infer a continuing decline for the purpose of applying Criterion C.
The species is found in localised subpopulations separated from large areas of unsuitable habitat, and there are no records of individuals moving large distances between habitat patches (de Melo Dantas & Albano 2018). The species is therefore thought to have small subpopulations with fewer than 1,000 mature individuals in each subpopulation (de Melo Dantas & Albano 2018). Condition a(i) is met at the level of Vulnerable. Less than 90% of individuals are found in any one subpopulation, meaning that the species does not meet condition a(ii). There is no evidence that the species’s population size is undergoing extreme fluctuations so the species doesn’t meet condition b.
Although the population size falls beneath the threshold for listing the species as Endangered under Criterion C, the population size is suspected to be declining, and condition a(i) is met at the level of Vulnerable, there is insufficient evidence to be able to infer a continuing decline. The species therefore qualifies as Near Threatened, approaching the threshold for listing as threatened under Criterion C2a(i).
Criterion D – Based on the population estimates described above (600-1,700 mature individuals), the species may qualify for listing as Vulnerable or Near Threatened under Criterion D1, depending on whether the true population size is most likely to be above, or below 1,000 mature individuals. The species does not have a restricted area of occupancy or number of locations such that a threat could drive the species to Critically Endangered or Extinct within a very short time. The species does not meet the criteria for listing as Vulnerable under Criterion D2.
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.
Based on the above assessment, it is proposed to list Forbes’s Blackbird (Anumara forbesi) as Vulnerable under Criterion D1. However, should evidence arise that indicates that the population size is more likely to be greater than 1,000 mature individuals, the species may be listed as Near Threatened under Criteria C2a(i); D1. We welcome any comments to the proposed listing. Information is particularly requested on the species’s population size and trend.
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.; Symes, A.; Taylor, J.; Šekercioğlu, Ç.; Butchart, S. H. M. (2020). Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology online first view.
de Melo Dantas, S. & Albano, C. 2018. Anumara forbesi (Sclater, 1886). In: Instituto Chico Mendes de Conservação da Biodiversidade (ed.), Livro Vermelho da Fauna Brasileira Ameaçada de Extinção: Volume III – Aves, pp. 566-568. Brasília.
Fraga, R.; Sharpe, C.J. 2016. Forbes’s Blackbird (Curaeus forbesi). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. and de Juana, E. (eds), Handbook of the Birds of the World Alive, Lynx Edicions, Barcelona.
Global Forest Watch. 2020. Interactive Forest Change Mapping Tool. Available at: http://www.globalforestwatch.org/.