Archived 2020 topic: Red-and-black Grosbeak (Caryothraustes erythromelas): revise global status?

BirdLife species factsheet for Red-and-black Grosbeak

The Red-and-black Grosbeak (Caryothraustes erythromelas) occurs in extreme eastern Venezuela, north and central Guyana, Suriname (except south-west), French Guiana and Brazil from Amapá south to Pará and Maranhão (del Hoyo et al. 2011, WikiAves 2015) and west across south Amazonian Brazil into the Madeira drainage in Rondônia (Fernandes 2007, A. Lees in litt. 2011, WikiAves 2015).

The species is found in the lower levels of pristine mature lowland humid forest, terre firme and seasonally flooded forest. Since it requires near pristine forest (del Hoyo et al. 1992), it is especially sensitive to fragmentation and disturbance, particularly as it is already rare and occurs at low densities. It is threatened by deforestation, and is currently listed as Near Threatened because it was projected to decline by a rate approaching 30% over the next three generations owing to deforestation in the Amazon, based on analyses in Bird et al. (2011) using the deforestation scenarios in Soares-Filho et al. (2006).

More recent remote-sensed data on deforestation have indicated that the rate has been lower than projected (Global Forest Watch 2020). Additionally, the species’s generation length has been re-estimated and is now thought to be slightly shorter (Bird et al. 2020)*, meaning that reductions under Criterion A are now calculated over ten years rather than 12. We are therefore reviewing the species’s Red List Category. Our current information on the conservation status will now be compared to all Red List Criteria.

Criterion A – The species’s generation length is now estimated to be 3.26 years, using the methodology of Bird et al. (2020)*, as applied to parameter values updated for use in the current reassessment cycle. This means that reductions should be assessed over a period of ten years for the application of Criterion A.

Remote-sensed data indicates that over ten years from 2009-2019, approximately 7% of tree cover was lost within the mapped range (Global Forest Watch 2020). 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). Assuming that the population size is proportional to area of tree cover, and taking into account the potential additional impact of disturbance, the population size is suspected to have undergone a reduction 7-11% over the past decade. The species is assessed as Least Concern under Criterion A2.

Over the period 2016-2019, approximately 4% of the total area of tree cover was lost. If this rate were to continue over the next ten years, this would amount to a loss of 10%. Assuming that the population size is proportional to area of tree cover, and that disturbance may increase the impact of deforestation by 51%, a population reduction of 7-15% is suspected over the next decade. This magnitude of reduction does not approach the thresholds for listing the species as threatened under Criterion A3 or A4. The species is therefore assessed as Least Concern under Criterion A.

Criterion B – Based on the area of a minimum convex polygon around the species’s entire mapped range, the Extent of Occurrence (EOO) is estimated at 2,530,000 km2. 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 considering the species’s large range, it is unlikely to approach the threshold for threatened under Criterion B2 (2000 km2).The species is assessed as Least Concern under Criterion B.

Criterion C  – The population size has not previously been estimated and no survey data are available, but it has been described as ‘uncommon and patchily distributed’ (Stotz et al. 1996, O. Ottema in litt. 2020), and is not present in all suitable habitat patches within its range (Thiollay 2002). Based on the minimum recorded population density of a congener (Caryothraustes canadensis, 2.1 individuals per km2; Thiollay 1986), the estimated area of forest within the range in 2010 (1,090,000 km2; Global Forest Watch 2020), and assuming 10-25% of the forest is occupied by the species, the population size is tentatively suspected to fall within the band 100,000 – 499,999 mature individuals. This does not approach the threshold for listing as threatened under Criterion C. The species is assessed as Least Concern under this criterion.

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 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.

Based on the above assessment, it is proposed to list the Red-and-black Grosbeak (Caryothraustes erythromelas) as Least Concern. However, should evidence arise that indicates that the species is likely to undergo a population reduction of 20% or more over the next decade, the species may be retained as Near Threatened.To allow us to achieve a clearer assessment of the species’s status, information is requested on the projected rate of population decline, and likely rate of deforestation within the species range, over the next decade.

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.

References

Barlow, J., Lennox, G. D., Ferreira, J., Berenguer, E., Lees, A. C., Mac Nally, R., Thomson, J. R., de Barros Ferraz, S. F., Louzada, J., Oliveira, V. H. F. and Parry, L. 2016. Anthropogenic disturbance in tropical forests can double biodiversity loss from deforestation. Nature 535(7610): 144-147.

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 in prep.

Bird, J. P.; Buchanan, J. M.; Lees, A. C.; Clay, R. P.; Develey, P. F.; Yépez, I.; Butchart, S. H. M. 2011. Integrating spatially explicit habitat projections into extinction risk assessments: a reassessment of Amazonian avifauna incorporating projected deforestation. Diversity and Distributions: doi: 10.1111/j.1472-4642.2011.00843.x.

del Hoyo, J.; Elliot, A.; Christie, D. 2011. Handbook of the birds of the world vol. 16: Tanagers to New World Blackbirds. Lynx Edicions, Barcelona.

Fernandes, A.F. 2007. Southern range extension for the Red-And-Black Grosbeak (Periporphyrus erythromelas, Cardinalidae), Amazonian, Brazil. Revista Brasileira de Ornitologia 15(3): 468-469.

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).

Soares-Filho, B.S., Nepstad, D.C., Curran, L.M., Cerqueira, G.C., Garcia, R.A., Ramos, C.A., Voll, E., McDonald, A., Lefebvre, P. and Schlesinger, P. 2006. Modelling conservation in the Amazon basin. Nature 440(7083): 520-523.

Stotz, D.F.; Fitzpatrick, J.W.; Parker, T.A.; Moskovits, D.K. 1996. Neotropical Birds: Ecology and Conservation. University of Chicago Press, Chicago.

Thiollay, J. M. 1986. Structure comparee du peuplement avien dans trois sites de foret primaire en Guyane. Revue d’Ecologie (La Terre et la Vie) 41: 59-105.

Thiollay, J.-M. 2002. Avian diversity and distribution in French Guiana: patterns across a large forest landscape. Journal of Tropical Ecology 18: 471–498.

WikiAves. 2015. Bicudo-encarnado. Available at: http://www.wikiaves.com.br/wiki/bicudo-encarnado. (Accessed: 28 April 2020).

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4 Responses to Archived 2020 topic: Red-and-black Grosbeak (Caryothraustes erythromelas): revise global status?

  1. Otte H. Ottema says:

    I agree to list the Red-and-black Grosbeak (Caryothraustes erythromelas) as Least Concern.

  2. Red List Team (BirdLife International) says:

    Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested by so many people in commenting. The window for consultation is now closed. We will analyse and interpret the new information and post a preliminary decision on this species’s Red List status on this page in early July.

    Thank you once again,
    BirdLife Red List Team

  3. Red List Team (BirdLife International) says:

    Preliminary proposal

    Based on available information, our preliminary proposal for the 2020 Red List would be to adopt the proposed classification outlined in the initial forum discussion.

    There is now a period for further comments until the final deadline in mid-July, 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 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  4. Red List Team (BirdLife International) says:

    Recommended categorisation to be put forward to IUCN

    The final categorisation for this species has not changed. Red-and-black Grosbeak is recommended to be listed as Least Concern.

    Many thanks for everyone who contributed to the 2020 GTB Forum process. The final 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021, following further checking of information relevant to the assessments by both BirdLife and IUCN.

Comments are closed.