Data Zone
Justification of Red List category
This species has a small population, which is restricted to gallery forests along the rio Branco and its tributaries. Rapid future declines are suspected due to proposed hydroelectric dams that could destroy a significant extent of remaining habitat, on top of ongoing moderately rapid rates of forest cover in this highly limited forest type. The remaining population is considered to be divided by habitat loss into separate and small subpopulations. The species is therefore listed as Vulnerable.
Population justification
Extensive playback surveys along the rivers in the Guyanese part of the range found a density of 45 mature individuals/km2 (South Rupununi Conservation Society 2021). Combining this with existing population estimates made by Vale et al. (2007) in the remainder of the species' range in Brazil (where density and occupancy estimates were broadly similar), a global population of c.6,600-16,600 mature individuals was extrapolated (South Rupununi Conservation Society 2021, B. O'Shea in litt. 2022). However, given the data used for estimating the habitat extent and population size in Brazil are 20 years old, an updated assessment is urgently required (South Rupununi Conservation Society 2021, B. O'Shea in litt. 2024). The population structure has not been formally investigated, but the species' absence from areas of suitable habitat suggests that degradation of gallery forest could well mean that there are now numerous small, disconnected populations, where the minimum population size of the largest falls below 1,000 mature individuals.
Trend justification
During surveys along rivers in Guyana, the species was absent from large tracts of seemingly suitable habitat where it had been observed previously (Vale et al. 2007, South Rupununi Conservation Society 2021, B. O'Shea in litt. 2022). It has been hypothesised that the population decline is caused by habitat loss as well as fires degrading and fragmenting habitat, leading to increasing isolation between populations (B. O'Shea in litt. 2022).
Over the past ten years, 7% of tree cover has been lost within the range; since 2017 this has been increasing to a rate equivalent to 10% over ten years (Global Forest Watch 2023, using Hansen et al. [2013] data and methods disclosed therein). The species may be disproportionately affected due to its strict habitat requirements, as its riverine habitat is easily accessible and thus highly susceptible to forest loss and degradation. To illustrate this, comparable surveys between 2004 and 2021 indicated a range contraction exceeding 50 linear kilometers along the Ireng (Maú) River (B. O'Shea in litt. 2024). Moreover, large parts of the range lie within the footprint of the proposed Bem Querer hydroelectric dam on rio Cotingo (Naka et al. 2020, Aleixo et al. 2023). This is scheduled for completion in 2031 and will flood a significant proportion of the species' habitat, with no prospect for the creation of new suitable areas. Tentatively, rates of population decline are suspected to have been within the band 15-25% over the past ten years, to accelerate to between 25-35% in the ten years from 2017 to 2027 and fall within the band 30-49% for the ten years to 2035 to account for the uncertain impact of the hydroelectric dams.
Cercomacra carbonaria is restricted to the rio Branco and some of its tributaries in Roraima, extreme north Brazil, and adjacent Guyana. It ranges along the rio Branco and rio Tacutu to the Ireng river in Guyana (Zimmer et al. 1997). It has been found on the rio Mucajaí, and also along the rio Parimé and the rio Uraricoera (Grosset and Minns 2002, Vale et al. 2007).
It is restricted to gallery forest within the floodplain of the rivers, consequently has a limited range and an estimated Area of Occupancy (AOO) is between 1,140 and 4,560 km2, based on a 2x2 km grid across the mapped range. This lies within an Extent of Occurrence of 56,700 km2. Patchy occurrence may mean that the lower bound of the potential AOO is more likely to be close to the true occupied area, with previous mapping of available habitat (at finer scale than that required for AOO) estimating only 723 km2 present (Vale et al. 2007). In addition, the AOO is inferred to be undergoing a continuing decline based on the moderate rate of forest cover loss within this range (Global Forest Watch 2023) and the observation from repeated surveys of the contraction by over 50 linear kilometers of the range along the Ireng (Maú) river between 2004-2021 (B. O'Shea in litt. 2024). With the threat posed by dam construction for hydroelectric power coupled with worsening fire impacts and ongoing forest cover loss due to clearance for agriculture and logging, a continuing decline in the area, extent and quality of habitat is inferred to be taking place. In addition, the number of locations is considered to be moderately small, between 11-20, and the impacts described above are inferred to indicate that there is also a continuing decline in this value.
The species occurs in dense, intact gallery forest along the river edge, within c.500 m from the river (Zimmer et al. 1997, South Rupununi Conservation Society 2021). On river islands it largely inhabits interior, densely wooded forest, with trees 20-30 m in height (Zimmer et al. 1997). It has also been found in dense second growth, consisting mostly of overgrown manioc plantations with widely scattered, 20-30 m trees (Zimmer et al. 1997). The diameter of territories is 100-150 m, and breeding is probably in the wet season (Zimmer et al. 1997).
The species is threatened by accelerating deforestation within its range as land is cleared for the expansion of small-scale agriculture and rice cultivation, as well as selective logging in gallery forests (Zimmer et al. 1997, 2020; Aleixo et al. 2023). Burning of habitat is a significant threat: In 1998, c. 75% of Ilha São Jose was burnt, and widespread fires in Roraima in 1999 probably had a severe impact on its river-edge habitats (A. Whittaker in litt. 1999). It is hypothesised that habitat degradation through fires caused population declines in Guyana (B. O'Shea in litt. 2022, 2024). Moreover, large parts of the range between Caracaraí and Boa Vista, Brazil, will be affected by the planned Bem Querer hydroelectric dam on rio Cotingo (Naka et al. 2020, Aleixo et al. 2023), scheduled for completion by 2031 (EPE 2024). Three additional small dams have also been proposed along the Mucajai River within the range of the species (Fearnside 2020).
Conservation Actions Underway
The species occurs within Viruá National Park. It is listed as Near Threatened at the national level in Brazil (Aleixo et al. 2023).
Conservation Actions Proposed
Research the species' ecology and response to habitat fragmentation, and assess its population structure. Research actions for the conservation of the species and its habitat. Monitor the population trend.
Expand the protected area network to effectively protect key sites. Protect river-island habitat and adjacent gallery forest on the mainland. Effectively manage protected areas, utilising emerging opportunities to finance protected area management with the joint aims of reducing carbon emissions and maximizing biodiversity conservation. Restore degraded areas to facilitate movement and gene flow. Raise awareness for the species with the aim of reducing pressures on its habitat. Mitigate the impacts of the planned hydroelectric dam on the species' habitat. Establish and expand ecotourism activities in the area. Incentivise conservation on private lands through expanding market pressures for sound land management and preventing forest clearance on lands unsuitable for agriculture (Soares-Filho et al. 2006).
15 cm. Mid-sized, long-tailed, black antbird. Male is mostly black with indistinct white streaking on throat and breast, white fringes to wing-coverts and tips to tail feathers. Female is dark slate-grey with white throat streaked dark grey and otherwise ochraceous underparts. Black wings and tail with white markings as in male. Voice Series of up to 20 defined pook or faster kikuk notes.
Text account compilers
Vine, J., Hermes, C.
Contributors
Capper, D., Mahood, S., O'Shea, B., Pople, R., Sharpe, C.J., Silveira, L.F., Symes, A., Vale, M., Westrip, J.R.S. & Whittaker, A.
Recommended citation
BirdLife International (2024) Species factsheet: Rio Branco Antbird Cercomacra carbonaria. Downloaded from
https://datazone.birdlife.org/species/factsheet/rio-branco-antbird-cercomacra-carbonaria on 22/11/2024.
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 22/11/2024.