BirdLife species factsheet for Black-polled Yellowthroat
Black-polled Yellowthroat (Geothlypis speciosa) is endemic to central Mexico. It inhabits lakeshores and freshwater marshes, where it requires extensive reedbeds. The population size is tentatively estimated at 1,500-7,000 mature individuals. The species has already been extirpated from several former sites and is currently only known from five lakes and wetlands within its range.
Black-polled Yellowthroat does not tolerate habitat modifications (S. N. G. Howell in litt. 1998), and thus the most severe threat is the loss of its wetland habitats. Marshes within the range have been greatly reduced in size, having been drained and planted with crops. Water levels are falling as a result of the drainage and a natural build-up of organic material.
The species has been considered Endangered under Criterion B1ab(i,ii,iii,iv,v) (BirdLife International 2020). 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 Red List criteria.
Criterion A – The species has been undergoing a large, significant decline over the past decades (Partners in Flight 2019), which is assumed to continue given the rapid degradation of wetlands. The rate of decline has been placed in the band 30-49% over ten years (one generation length being 2.4 years; Bird et al. 2020)*. Therefore, Black-polled Yellowthroat is assessed as Vulnerable under Criterion A2bc+3bc+4bc.
Criterion B – The newly calculated Extent of Occurrence (EOO) for this species is 14,300 km2. This meets the threshold for Vulnerable under Criterion B1. To be listed under this criterion does require at least two further conditions to be met though.
The species is known to occur at five wetlands within its range (Pérez-Arteaga et al. 2018). As the largest threat to the species is the drainage of its wetland habitat, we can conclude that each wetland represents one separate location**, and that consequently the species occurs at 5 locations*. Hence, condition a is met at the level of Endangered and Vulnerable. Given the ongoing threats, we can assume that there is an ongoing decline in the species’s EOO, AOO, quality/extent of habitat and number of locations** of occurrence, 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.
Overall, while the EOO is too large to list the species as Endangered, it triggers sufficient conditions for Vulnerable. Therefore, Black-polled Yellowthroat is assessed as Vulnerable under Criterion B1ab(i,ii,iii,iv,v).
Criterion C – The population is estimated to number 1,500-7,000 mature individuals and inferred to be in decline, as the loss of suitable habitat has extirpated the species from former sites. This meets the threshold for listing as threatened under Criterion C2. However, in order to be listed under this criterion, further conditions must be met.
Given its disjunct range, it is conceivable that the species forms several subpopulations. Thus, condition a(ii) is not met. Nevertheless, given the overall population size it is unlikely that these subpopulations number less than 250 mature individuals each. It is however possible that each subpopulation consists of less than 1,000 mature individuals. Consequently, condition a(i) is met at the level of Vulnerable. The population size is not thought to undergo severe fluctuations, and thus condition b is not met. As such, Black-throated Yellowthroat qualifies for listing as Vulnerable under Criterion C2a(i).
Criterion D – The species’s population has been placed in the band 1,500-7,000 mature individuals. Under the assumption that the true population size is closer to the lower end of the estimate, Black-polled Yellowthroat may be listed as Near Threatened, approaching the threshold for listing as threatened under Criterion D1.
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 suggested that the species be listed as Vulnerable under Criteria A2bc+3bc+4bc; B1ab(i,ii,iii,iv,v); C2a(i). We welcome any comments to the proposed listing.
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. 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).
**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.
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.
BirdLife International. 2020. Species factsheet: Geothlypis speciosa. http://www.birdlife.org (Accessed 17 February 2020).
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. www.iucnredlist.org/technical-documents/categories-and-criteria.
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.
Pérez-Arteaga, A.; Monterrubio-Rico, T.; Delgado-Carrillo, O.; Cancino-Murillo, R.; Salgado-Ortiz, J. 2018. Updating the distribution range of the endangered Black-polled Yellowthroat (Geothlypis speciosa). Ornitología Neotropical 29: 51-57