Tanygnathus sumatranus (with subspecies sangirensis) and T. everetti (with subspecies burbidgii; race duponti synonymised with nominate) (Handbook of the Birds of the World and BirdLife International 2020) have been split from T. sumatranus (del Hoyo et al. 2014).
The assessment against the Tobias criteria (Tobias et al. 2010) in diagnosing the split is given here, from Arndt et al. (2019). In both sexes Philippine forms differ by their larger bills (effect size of everetti vs. sangirensis 1.62 and vs. sumatranus 1.15; effect size of burbidgii vs. sangirensis 1.75 and vs. sumatranus 2.02; as burbidgii is here treated as conspecific with everetti, the lower values for everetti must be considered, hence score 1); blood-red or orange-red vs. yellowish-white irides (3); pale matt royal blue in place of slightly glossy turquoise-blue lower back and rump (2); paler green head (ns); and duller green underparts (ns).
Moreover, in males the Philippine forms further differ by their absence of blue in the carpal feathers and scapulars (2); and much darker green mantle (ns). Philippine birds thus reach a total of 8 under the Tobias criteria, and achieve species rank as a consequence. The difference in wing length between everetti and burbidgii yields an effect size of 3.32. The difference in tail length between nominate sumatranus and sangirensis yields an efect size of 3.70. Both these findings point to the distinctness and validity of the forms burbidgii and sangirensis; burbidgii is larger in all dimensions than any other taxon except the little-known freeri (see below), while sangirensis almost matches it for wing length and almost matches everetti for tail length while exactly matching nominate sumatranus for bill length. It is also worth noting that the four Peleng and Banggai birds proved to have shorter wings and tails than any other taxa, and that the four Sula birds had larger bills than either sumatranus or sangirensis. Additionally, phylogenetic reconstruction identified the Philippine and Indonesian clades as being as genetically distinct as T. lucionensis and T. megalorynchos.
Handbook of the Birds of the World and BirdLife International. 2020. Handbook of the Birds of the World and BirdLife International digital checklist of the birds of the world. Version 5. Available at: http://datazone.birdlife.org/userfiles/file/Species/Taxonomy/HBW-BirdLife_Checklist_v5_Dec20.zip.
Red List criteria met
Red List history
IUCN Red List criteria met and history
||not a migrant
Population justification: The population is thought to be highly fragmented and extremely rare (L. M. J. Paguntalan in litt. 2020, P. Widmann in litt. 2020). Thus, the species is thought to number far less than 2,500 mature individuals, and possibly even less than 250 (P. Widmann in litt. 2020). Accounting for the lack of species's records in recent years however, the population is placed here in the band of 250-999 mature individuals, roughly converted to 375-1500 individuals.
Trend justification: Trapping for the cagebird and pet trade is one of the major threats towards the species (P. Widmann in litt. 2020). Habitat degradation due to the illegal cutting of trees (particularly across Tawi-Tawi which holds the majority of the species's population) is also accelerating population declines (G. Jakosalem in litt. 2020). Recent forest loss analyses (Global Forest Watch 2020) for example show that the the species may be declining at a rate of c. 13% over a three generation period (14.4 years; Bird et al. 2020), assuming that the population declines at the same rate as forest loss. Thus, although the species may occur in degraded forests (similar to the Azure-rumped Parrot), with the combined effect of trapping and habitat degradation, the species is inferred to be undergoing a continued decline of 10-19% over a three-generation period.
Important Bird and Biodiversity Areas (IBA)
BirdLife International (2023) Species factsheet: Tanygnathus everetti. Downloaded from
http://datazone.birdlife.org/species/factsheet/blue-backed-parrot-tanygnathus-everetti on 04/12/2023.
Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from
http://datazone.birdlife.org on 04/12/2023.