BirdLife species factsheet for Azure-rumped Tanager: http://datazone.birdlife.org/species/factsheet/azure-rumped-tanager-tangara-cabanisi
This discussion was first published as part of the 2019 Red List update. At the time a decision regarding the status of this species was pended, but to enable potential reassessment of this species as part of the 2020 Red List update this post remains open and the date of posting has been updated.
Azure-rumped Tanager (Tangara cabanisi) occurs in the Sierra Madre de Chiapas of southern Mexico, and in south-western Guatemala (Heath and Long 1991, Collar et al. 1992, Eisermann et al. 2011). It is suggested to have a restricted distribution (see Cooper 2003, Eisermann and Avendaño 2007, Eisermann et al. 2011), within which it is locally common (M. Thompson in litt. 1998, Cooper 2003, Eisermann et al. 2011). It inhabits evergreen broadleaf forest (at 1,000-1,700m in Mexico, 860-1,900m in Guatemala), although has also been reported from plantations and edge habitat (Eisermann et al. 2011, Hilty and de Juana 2018). The species’s altitudinal range coincides with the best land for coffee growing, and while it does occur in plantations it is absent from the interior of intensive agriculture (Eisermann et al. 2011).
The species has been considered Endangered under Criterion B1ab(i,ii,iii,v) (see BirdLife International 2018). However, this is no longer tenable because this was based on an Extent of Occurrence (EOO) value calculated as the ‘area of mapped range’. This is no longer appropriate and the EOO should be calculated using a Minimum Convex Polygon (see IUCN 2001, 2012, Joppa et al. 2016), as EOO is a measure of the spatial spread of areas occupied by a species, not the actual area it occupies. The resulting EOO value now exceeds the thresholds required to maintain the species’s current listing, and as such it potentially cannot retain its current Red List status. Therefore, we have fully reviewed the species here against all criteria.
The initial topic on this analysis can be found here.
Criterion A – The population trend for this species has not been directly estimated. However, deforestation data from between 2000 and 2012 (Tracewski et al. 2016) suggests that the area of suitable habitat for the species on average is declining by c.1.7% over three generations (14.7 years). Therefore, while it may be possible to consider the species to be in decline, the rate of decline is likely to be slow and would not approach the threshold for Vulnerable under this criterion. Therfore, Azure-rumped Tanager is assessed as Least Concern under Criterion A.
Criterion B – The newly calculated Extent of Occurrence (EOO) for this species is 10,400 km2. Tracewski et al. (2016) estimated the maximum Area of Occupancy (AOO) (calculated as the remaining tree area within the species’s range) to be c.2,520 km2. Therefore, the EOO meets the threshold for Vulnerable under Criterion B1, while the AOO approaches the threshold for Vulnerable under Criterion B2. To be listed under this criterion does require further conditions to be met though.
Given the ongoing threats, we can assume that there is an ongoing decline in the species’s EOO, AOO and quality/extent of habitat, and can infer an ongoing population decline too. Therefore, conditions b(i,ii,iii,v) are met. However, the species is not known to undergo extreme fluctuations and so does not trigger condition c).
The species has been suggested to occur at only a limited number of localities (see BirdLife International 2018), yet records from eBird show a wider spread of records (eBird 2018). Based on IUCN definitions, the number of locations* where the species occurs is unlikely to meet the required thresholds. The species should not be considered severely fragmented per IUCN definitions (see IUCN Standards and Petitions Subcommittee 2017), although there is likely to be a degree of fragmentation of its habitat.
Thus, the species does not trigger sufficient conditions for listing as threatened under Criterion B. That said, it is possible that it approaches the thresholds required. As such, at worst, it may be very precautionarily thought to warrant listing as Near Threatened under Criteria B1ab(i,ii,iii,v)+2ab(i,ii,iii,v), although even this would be highly precautionary.
Criterion C – Based on surveys by Eisermann et al. (2011), the population in Guatemala is estimated to number 8,250-23,250 individuals (roughly equivalent to 5,500-15,500 mature individuals). However, the densities used in this study were from surveys at 1,400-1,900 m, where the species is most abundant. Therefore, the overall population size could fall either side of the threshold for Vulnerable (10,000 mature individuals), and precautionarily it could be estimated to be in the band 2,500-19,999 mature individuals to represent this uncertainty. Intuitively, this means that at the lower end of the band the species would meet the threshold for Vulnerable, but other conditions are required to warrant listing under Criterion C.
The rate of decline in the species has not been directly estimated, and so Criterion C1 cannot be used. The species is not known to undergo extreme fluctuations, so it does not trigger the conditions for Criterion C2b. The map of sightings of this species on eBird suggests that the species occurs in either one or two subpopulations. If it were to be considered as two subpopulations, then the species would likely not warrant listing under Criterion C at all, as the largest subpopulation would probably contain significantly greater than 1,000 mature individuals. On the other hand, it could be precautionary to suggest that the species only occurs in one subpopulation, and then it would warrant a listing of Vulnerable under Criterion C2a(ii).
Criterion D – The species’s population size and range are likely too large to warrant listing under this criterion. Therfore, Azure-rumped Tanager is assessed as Least Concern under Criterion D.
Criterion E – To the best of our knowledge, there has been no quantitative analysis of extinction risk conducted for this species. Therefore, it cannot be assessed against this criterion.
Therefore, it is precautionarily suggested that the species be listed as Vulnerable under Criterion C2a(ii). If further information or comment suggests that the species be considered to be in more than one subpopulation then, at worst, the species should be considered Near Threatened and potentially Least Concern. We welcome any comments, but 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’ Red List status. Therefore, please make sure your comments are relevant to the species’ Red List status and the information requested.
*The term ‘location’ refers to a distinct area in which a single threatening event can rapidly affect all individuals of the taxon present, with the size of the location depending on the area covered by the threatening event. Where a taxon is affected by more than one threatening event, location should be defined by considering the most serious plausible threat (IUCN 2001, 2012).
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.
BirdLife International. 2018. Species factsheet: Tangara cabanisi. Downloaded from http://www.birdlife.org on 27/09/2018.
Collar, N. J.; Gonzaga, L. P.; Krabbe, N.; Madroño Nieto, A.; Naranjo, L. G.; Parker, T. A.; Wege, D. C. 1992. Threatened birds of the Americas: the ICBP/IUCN Red Data Book. International Council for Bird Preservation, Cambridge, U.K.
eBird. 2018. eBird: An online database of bird distribution and abundance [web application]. eBird, Ithaca, New York. Available: http://www.ebird.org. (Accessed: Date [e.g., February 2, 2012]).
Eisermann, K.; Arbeiter, S.; López, G.; Avendaño, C.; Lux, J. de L. 2011. Distribution, habitat use and implications for the conservation of the Globally Threatened Azure-rumped Tanager Tangara cabanisi in Guatemala. Bird Conservation International 21: 423-437.
Eisermann, K.; Avendaño, C. 2007. Áreas propuestas para la designación como IBA (Área Importante para la Conservación de Aves) en Guatemala, con una priorización para la conservación adentro de las IBAs y una evaluación de las IBAs para aves migratorias Neárticas-Neotropicales.
Heath, M. F.; Long, A. J. 1991. Habitat, distribution and status of the Azure-rumped Tanager Tangara cabanisi in Mexico. Bird Conservation International 1: 223-254.
Hilty, S.; de Juana, E. 2018. Azure-rumped Tanager (Tangara cabanisi). 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 https://www.hbw.com/node/61676 on 28 September 2018).
IUCN. 2001. IUCN Red List Categories and Criteria: Version 3.1. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K.
IUCN. 2012. IUCN Red List Categories and Criteria: Version 3.1. Second edition. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge, U.K. Available at: www.iucnredlist.org/technical-documents/categories-and-criteria.
IUCN Standards and Petitions Subcommittee. 2017. Guidelines for Using the IUCN Red List Categories and Criteria. Version 13. Prepared by the Standards and Petitions Subcommittee. Downloadable from http://www.iucnredlist.org/documents/RedListGuidelines.pdf.
Joppa, L. N.; Butchart, S. H. M.; Hoffmann, M.; Bachman, S. P.; Akçakaya, H. R.; Moat, J. F.; Böhm, M.; Holland, R. A.; Newton, A.; Polidoro, B.; Hughes, A. 2016. Impact of alternative metrics on estimates of extent of occurrence for extinction risk assessment. Conservation Biology 30: 362-370.
Tracewski, Ł.; Butchart, S. H. M.; Di Marco, M.; Ficetola, G. F.; Rondinini, C.; Symes, A.; Wheatley, H.; Beresford, A. E.; Buchanan, G. M. 2016. Toward quantification of the impact of 21st-century deforestation on the extinction risk of terrestrial vertebrates. Conservation Biology 30: 1070-1079.