BirdLife International factsheet for Blue-backed Parrot.
Following a taxonomic reassessment, Blue-backed Parrot (Tanygnathus sumatranus) has been split into Azure-rumped Parrot (T. sumatranus) and Blue-backed Parrot (T. everetti) (see Arndt et al., 2019). The newly-split Blue-backed Parrot is found in the Philippines, while Azure-rumped Parrot is extant in Indonesia (Arndt et al., 2019).
The exact habitat requirements for the newly-split T. everetti have not been investigated, but it is very likely to inhabit tropical, lowland and montane forests, similar to T. sumatranus (del Hoyo et al., 1997). These species may also inhabit mangrove swamps, and can also tolerate degraded forests (del Hoyo et al., 1997). The population size of the pre-split species is unknown, but it is described as common to very common (del Hoyo et al., 1997). These species are not known to have many threats, but they may be at risk of habitat loss from deforestation (Tracewski et al., 2016).
The pre-split species was previously listed as Least Concern (BirdLife International, 2020). However, following the taxonomic split, new range sizes suggest that both species warrant a thorough reassessment. We have therefore reassessed both species against each criterion here.
IUCN guidelines stipulate that rates of decline should be measured over the longer of 10 years or 3 generations (IUCN Standards and Petitions Committee, 2019). The generation length for Blue-backed Parrot has been recalculated to 4.8 years (Bird et al., 2020)*. Therefore, the rates of reduction for these species are calculated over 14.4 years
Azure-rumped Parrot: The population trend for this species has not been directly estimated, but is now suspected to be in decline due to ongoing habitat loss (Tracewski et al. 2016). According to data from Global Forest Watch (2020), tree cover loss across this species’ post-split range between 2000-2018 was 13%. Estimating the effect on population decline is difficult, especially as this species seems to tolerate slightly degraded forest. However, even assuming that the population declines at the same rate as tree cover loss, this equates to a decline rate of 10% over three generations. Tracewski et al., (2016) also found low rates of deforestation in their analysis. This decline rate does not meet the threshold for threatened (≥30% decline over 3 generations) under this criterion. Azure-rumped Parrot may therefore be considered Least Concern under criterion A.
Blue-backed Parrot: This newly-split species may also be at risk from deforestation. Between 2000-2018, 6.2% of tree cover was lost across this species’s range (Global Forest Watch, 2020). Again, assuming that the population declines at the same rate as habitat loss, this equates to a decline rate of 5% over three generations. This rate of decline does not meet the threatened threshold here, so Blue-backed Parrot may be considered Least Concern under criterion A.
Azure-rumped Parrot: The newly-calculated EOO for T. sumatranus is 657,207 km². This is too high to trigger the threatened threshold and therefore, Azure-rumped Parrot may be considered Least Concern under criterion B.
Blue-backed Parrot: The newly-calculated EOO for T. everetti is 829,044 km². This is too high to trigger the threatened threshold (EOO <20,000 km²), and therefore, Blue-backed Parrot may be considered Least Concern under criterion B.
The population size for these species have not been estimated, but the pre-split T. sumatranus was described as common to very common (del Hoyo et al. 1997). A congener, the Blue-naped Parrot, T. lucionensis, was found at a population density of 11.29 individuals/km² on one Indonesian island (Riley, 2003). Assuming that T. sumatranus and T. everetti are also found at similar densities, and that 10% of their large ranges are occupied, the populations for both species would be far greater than the threshold of 10,000 mature individuals to qualify as threatened under this criterion. Therefore, both Azure-rumped Parrot and Blue-backed Parrot may be considered Least Concern under criterion C.
The population size for these species, based range sizes and the density estimates of a congener, are likely to be far higher than the threshold of 1000 mature individuals needed to qualify as threatened here. Both T. sumatranus and T. everetti may be considered Least Concern under criterion D.
To the best of our knowledge, no quantitative analysis has been carried out for these species and so they cannot be assessed against this criterion.
We therefore suggest that both Azure-rumped Parrot (Tanygnathus sumatranus) and Blue-backed Parrot (Tanygnathus everetti) 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.
Arndt, T., Collar, N. J., and Wink, M., 2019, The taxonomy of Tangynathus sumatranus, Bulletin of the British Ornithologists’ Club, 139(4), pp. 346-354
Bird, J.P., Martin, R., Akçakaya, H.R., Gilroy, J., Burfield, I.J., Garnett, S., 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. Online first view.
BirdLife International (2020) Species factsheet: Tanygnathus sumatranus. Downloaded from http://www.birdlife.org on 19/05/2020
del Hoyo, J.; Elliott, A.; Sargatal, J. 1997. Handbook of the Birds of the World, Vol. 4: Sandgrouse to Cuckoos. Lynx Edicions, Barcelona, Spain.
Global Forest Watch. 2020. World Resources Institute. http://www.globalforestwatch.org (Accessed 19 May 2020).
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
Riley, J., 2003, Population sizes and the conservation status of endemic and restricted-range bird species on Karakelang, Talaud Islands, Indonesia, Bird Conservation International, 13, pp: 59–74.
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.