Blue-backed Parrot (Tanygnathus sumatranus) is being split: assessment of newly recognised taxa.

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.

Criterion A:

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.

Criterion B:

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.

Criterion C:

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.

Criterion D:

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.

Criterion E:

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.

References

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.

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6 Responses to Blue-backed Parrot (Tanygnathus sumatranus) is being split: assessment of newly recognised taxa.

  1. Peter Widmann says:

    This refers to Tanygnathus everetti:
    This species was probably for a long time much less common than T. sumatranus. “Once widespread and fairly common, but now very rare through most of its range except the Sulus” (Kennedy et al. 2000). The species was never encountered by us on Polillo during the early 2000s during cumulative six weeks of cockatoo field work, also no record from Siargao Island during 26 days of field work in 2016 and 2017. Its encounter rate was only 0.28 ind./person days during seven days of fieldwork in southern and central Samar (same as for Philippine Cockatoo, two individuals observed respectively during seven days). It probably has disappeared over large parts of its range, particularly Luzon and the Western Visayas. Recent observations (e.g. in Ebird) are very scarce and from very few locations (Tawi-Tawi, eastern Mindanao, central Samar, a single record from SW Mindanao), suggesting that AOO is now very small, likely qualifying for Endangered under category B2. (a).
    The newly calculated EOO is therefore almost certainly way too optimistic. It is also not feasible to use population density estimates for T. lucionensis, particularly not from Talaud, where the densities are comparably high; this species is much rarer in the rest of the range (except Palawan), but can be found still in higher densities than T. everetti, where they occur together.
    The species was heavily trapped for the pet trade in the early 2000s in Samar and probably elsewhere so that decline was likely much steeper than suggested by the loss of habitat alone. Each poacher family reported to capture ca. 50 parrots per month during the season (several species).
    Given the very few and small remaining habitats and the very low encounter rates, it is probable that there are less than 2,500 mature individuals left, and it is not inconceivable that there are less than 250 under criterion C. Surveys are definitely urgently needed.

  2. Red List Team (BirdLife International) says:

    The following comment has been submitted by Desmond Allen via email:

    4 races:
    duponti – no recent records probably extinct.
    freeri – no recent records probably extinct.
    everetti – probably extinct over most of its range. Only recent records from Agusan del sur and Samar.
    burbidgii – another split? – hanging on in remaining and dwindling tall forest of Tawi Tawi. Strip mining for nickel by Chinese companies is reducing habitat.

    Least Concern is unlikely. Situation similar to Philippine cockatoo some years ago. A favourite of the bird trade.

  3. Simon Mahood says:

    “These species are not known to have many threats, but they may be at risk of habitat loss from deforestation (Tracewski et al., 2016). ” Poaching of adults and nestlings for the cagebird trade should be added to the list of known threats to parrots in Indonesia and the Philippines.

  4. James Eaton says:

    Judging by severe lack of recent records, and massive deforestation in two of the more regular areas (Eastern Mindanao and Samar), surely Blue-backed Parrot would be a Critically Endangered listing. Sadly, I have no hard data to back this up, but the recent numbers suggest this bird is more threatened than Philippine Cockatoo.
    The last stronghold, on Tawi-tawi will be under the same pressures as both Sulu Hornbill and Blue-winged Racquet-tail, both of which are CR.

    It would be nice to hear from Philippine-based birders regarding the true extend of decline.
    On a visit to Samar, in 2004 the species was already extremely difficult to find in the forest, but we saw many birds kept as pets in local houses.

    Azure-rumped Parrot appears to be less affected by parrot trade than other Indonesian parrot species – though is still trapped, and still reasonably widespread, and fairly common on certain islands, but this could easily change.

    James

  5. Red List Team (BirdLife International) says:

    Many thanks to everyone who has contributed to this discussion. We greatly appreciate the time and effort invested by so many people in commenting. 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 once again,
    BirdLife Red List Team

  6. Red List Team (BirdLife International) says:

    Preliminary proposal

    Based on available information and the known rarity of the Blue-backed Parrot, the population size has been re-estimated into the band of 1,000-2,499 mature individuals (as per P. Widmann in litt. 2020). The species also holds a stronghold in only one locality, the Tawi-Tawi region of Philippines, with likely scarcer occurrences in Eastern and Southwestern Mindanao, and Central Samar (eBird, 2020). The species is also considered to be undergoing significant declines due to heavy deforestation.

    Thus, our preliminary proposal for the 2020 Red List would be to list

    Azure-rumped Parrot as Least Concern

    Blue-backed Parrot as Endangered under Criterion C2a(i).

    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 the initial proposal.

    The final 2020 Red List categories will be published on the BirdLife and IUCN websites in December 2020/January 2021 (information on the IUCN Red List update process can be found here), following further checking of information relevant to the assessments by both BirdLife and IUCN.

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