Archived 2020 topic: Pink-headed Warbler (Cardellina versicolor): revise global status?

BirdLife species factsheet for Pink-headed Warbler

Pink-headed Warbler (Cardellina versicolor) occurs in the mountains of Chiapas, Mexico, and western Guatemala. It inhabits oak-alder-conifer forest, scrub and cloud forest at elevations of 1,800-3,500 m. The species prefers humid forests with undisturbed understorey, but is also found in disturbed forests and open or edge habitat (Curson et al. 1994, Howell and Webb 1995, K. Eisermann in litt. 2012, Curson 2020). The global population is thought to number 20,000-50,000 individuals (Curson 2020), which roughly equates to 13,000-33,000 mature individuals. The species is rare and local in parts of its range in Chiapas, but locally common in Guatemala (Eisermann and Avendaño 2007, Curson 2020) and remains regularly recorded throughout the range (eBird 2020).

Pink-headed Warbler is threatened by the loss and degradation of its habitat and has undergone declines in the past (Curson 2020). Only 400 km2 of cloud forest, which is among the preferred habitats for the species, remain in central Chiapas and 900 km2 in Guatemala, representing 3% of the original extent (Curson 2020).

The species has been considered Vulnerable under Criterion B1ab(i,ii,iii,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 criteria.

Criterion A – The population trend for this species has not been directly estimated, but the species is suspected to be in slow decline owing to habitat degradation. Deforestation data from between 2000 and 2012 (Tracewski et al. 2016; see also Global Forest Watch 2020) suggests that the area of suitable habitat for the species on average is declining by c.2.6% over ten years (one generation length being 2.4 years; Bird et al. 2020*). Pink-headed Warbler prefers undisturbed forest, but appears to tolerate edges and degraded habitat. Therefore, while it may be possible to consider the species to be in decline, the rate of population decline is unlikely to exceed the rate of forest loss, not approaching the threshold for Vulnerable under Criterion A. Therefore, Pink-headed Warbler is assessed as Least Concern under this criterion.

Criterion B – The newly calculated Extent of Occurrence (EOO) for this species is 52,900 km2. This is too large to meet the threshold for Vulnerable under Criterion B1, and Pink-headed Warbler may be listed as Least Concern under this criterion. The Area of Occupancy (AOO) has not been quantified following IUCN Guidelines (IUCN Standards and Petitions Committee 2019), and therefore the species cannot be assessed against Criterion B2.

Criterion C – The global population of Pink-headed Warbler is thought to number 13,000-33,000 mature individuals.  This is too large to warrant listing as threatened under Criterion C. However, assuming that the true population size is closer to the lower end of the estimate and given that the species is suspected to be in decline, however, it is likely that the population size approaches the threshold for Vulnerable under this criterion (<10,000 mature individuals). Yet, in order to be listed as Near Threatened under Criterion C, other conditions have to be met.

The rate of decline in the species has not been directly estimated, and so Criterion C1 cannot be used. Based on known records (eBird 2020), Pink-headed Warbler is thought to occur in a small number of subpopulations (potentially three to five). These subpopulations likely consist of more than 1,000 mature individuals each; so the species does not meet the conditions 2a(i) or 2a(ii). Moreover, the species is not known to undergo extreme fluctuations, and thus does not trigger condition 2b. Therefore, Pink-headed Warbler may be listed as Least Concern under Criterion C.

Criterion D – The species’s population size and range are too large to warrant listing as threatened, and thus Pink-headed Warbler may be considered 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 suggested that the Pink-headed Warbler (Cardellina versicolor) be listed as Least Concern.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).

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

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: Cardellina versicolor. http://www.birdlife.org (Accessed 18 February 2020).

Curson, J. 2020. Pink-headed Warbler (Cardellina versicolor). 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, Spain. https://www.hbw.com/node/61526 (Accessed 18 February 2020).

Curson, J.; Quinn, D.; Beadle, D. 1994. New World warblers. A&C Black/Christopher Helm, London, UK.

eBird. 2020. eBird: An online database of bird distribution and abundance [web application]. eBird, Ithaca, NY, USA. http://www.ebird.org (Accessed 18 February 2020).

Eisermann, K.; Avendaño, C. 2007. Lista comentada de las aves de Guatemala – Annotated checklist of the birds of Guatemala. Lynx Edicions, Barcelona, Spain.

Global Forest Watch. 2020. World Resources Institute. http://www.globalforestwatch.org (Accessed 18 February 2020).

Howell, S. N. G.; Webb, S. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, Oxford, UK.

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.

IUCN Standards and Petitions Committee. 2019. Guidelines for using the IUCN Red List Categoreis and Criteria. Version 14. 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.

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4 Responses to Archived 2020 topic: Pink-headed Warbler (Cardellina versicolor): revise global status?

  1. Red List Team (BirdLife International) says:

    Global Forest Change data on tree cover loss up to 2019 have now been released and made available via Global Forest Watch. Based on these data, over ten years approximately 3.3% of tree cover with 75% canopy cover was lost from within the species’s range (Global Forest Watch 2020). This does not affect the above assessment under Criterion A.

  2. Red List Team (BirdLife International) says:

    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,
    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. Pink-headed Warbler 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.