Systematics
Some of the species listed here are occasionally placed in the genera Agyrtria, Polyerata and Saucerottia. But most authorities, notably the SACC, do not accept the validity of these until more comprehensive studies are available, instead placing them all in Amazilia. The IUCN and BirdLife International, after splitting up the genus Amazilia for some time, have followed the SACC's argument and treats these hummingbirds as a single genus until enough data is available for a thorough revision.
But regardless, the present arrangement is only temporary; it is generally recognized that Amazilia in the broad definition is overly inclusive and perhaps not even monophyletic, and that some species would be better moved to one or more distinct genera. However, the monophyly of the proposed additional genera is not conclusively established either.
Two additional species in Amazilia are sometimes included in Leucippus today as they are markedly distinct, but this placement requires confirmation. These are the White-bellied Hummingbird (A. chionogaster) and the Green-and-white Hummingbird (A. viridicauda).
Read more about this topic: Amazilia