The three species over the genus Zanda are actually variously regarded as two, then as one species for rather a while. In the 1979 paper, Australian ornithologist Denis Saunders highlighted the similarity between the small-billed along with the southern race xanthanotus within the yellow-tailed and dealt with them as one https://franciscoeuman.articlesblogger.com/58884166/umbrella-cockatoo-cost-no-further-a-mystery