The taxonomy of Tanygnathus sumatranus

Philippine taxa currently assigned to Blue-backed, Azure-rumped or Müller'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).