BirdLife species factsheet for Apo Sunbird
Apo Sunbird (Aethopyga boltoni) is endemic to Mindanao, Philippines. It occurs in mossy forests above 1,500 m, where it is found near flowering trees shrubs. The species is described as fairly common (Cheke et al. 2001). Assuming that the species occurs at the same density as a congener, Lovely Sunbird A. shelleyi (49.1 individuals/km2; Santini et al. 2018), Apo Sunbird might number c. 368,000 individuals, roughly equating to 245,000 mature individuals. Forests within the range of Apo Sunbird are not thought to be under imminent threat (Cheke et al. 2001, see also Tracewski et al. 2016, Global Forest Watch 2020) and the species is thought to be stable.
Apo Sunbird has been considered Near Threatened, approaching the threshold for listing as threatened under Criterion B1ab(iii) (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 is thought to be stable. The only threat known to Apo Sunbird is habitat loss, but forest loss within the range has been very low (<5% over ten years; Bird et al. 2020*; see Tracewski et al. 2016, Global Forest Watch 2020). Therefore, Apo Sunbird may be listed as Least Concern under Criterion A.
Criterion B – The newly calculated Extent of Occurrence (EOO) for this species is 31,600 km2. This is too large to meet the threshold for Vulnerable under Criterion B1, and Apo Sunbird 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 size is too large to warrant listing as threatened under this criterion, and therefore Apo Sunbird is considered Least Concern under Criterion C.
Criterion D – The global population size and range are too large to warrant listing as threatened under this criterion, and therefore Apo Sunbird is 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 Apo Sunbird (Aethopyga boltoni) 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.
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: Aethopyga boltoni. http://www.birdlife.org (Accessed 28 February 2020).
Cheke, R. A.; Mann, C. F.; Allen, R. 2001. Sunbirds: a guide to the sunbirds, flowerpeckers, spiderhunters and sugarbirds of the world. Christopher Helm, London, U.K.
Global Forest Watch. 2020. Interactive Forest Change Mapping Tool. http://www.globalforestwatch.org (Accessed 18 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.
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.
Santini, L.; Isaac, N. J. B.; Ficetola, G. F. 2018. TetraDENSITY: A database of population density estimates in terrestrial vertebrates. Global Ecology and Biogeography 27: 787-791.
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.