The taxonomy of Tanygnathus sumatranus

Philippine taxa currently assigned to Blue-backed, Azure-rumped or Muller's Parrot Tanygnathus sumatranus are distinctive both morphologically (larger bill, red vs. pale yellow iris, royal blue vs. glossy turquoise-blue rump, paler green head and duller green underparts; and males having darker green mantles and no blue on the carpals and scapulars) and genetically (as distinct from Indonesian T. sumatranus as T. lucionensis is from T. megalorhynchos). We therefore propose T. everetti (with subspecies burbidgii and freeri; race duponti synonymised with nominate) to be elevated to species rank with the name Blue-backed Parrot, leaving Indonesian T. sumatranus (with subspecies sangirensis) as Azure-rumped Parrot. The taxonomic status of T. e. burbidgii (Sulu Islands) and T. s. sangirensis (Talaud Islands), both notably larger than their respective nominates, deserves study.