The blue-tailed emerald (Chlorostilbon mellisugus) is a hummingbird in the "emeralds", tribe Trochilini of subfamily Trochilinae. It is found in tropical and subtropical South America east of the Andes from Colombia east to the Guianas and Trinidad, and south to northern Bolivia and central Brazil.
Taxonomy and systematics
The blue-tailed emerald was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under the binomial name Trochilus mellisugus. The specific epithet combines the Latin mel meaning "honey" and sugere meaning "to suck". Linnaeus's description was typically brief and it was unclear which species he was describing. When he updated his Systema Naturae for the twelfth edition in 1766 Linnaeus added citations including one to the "all-green humming-bird" that had been described and illustrated by the English naturalist George Edwards in his Gleanings of Natural History. The identity still remained uncertain but in 1950 the American ornithologist John T. Zimmer argued that the species Trochilus mellisugus described by Linnaeus could only have been the blue-tailed emerald. This has been generally accepted.
The blue-tailed emerald has at times had as many as 17 subspecies assigned to it. Most of them have been reevaluated as individual species, as subspecies of other species, or as not being distinguishable at all.
Three major worldwide taxonomic systems differ in their treatment of the species. The International Ornithological Committee (IOC) recognizes seven subspecies. The Clements taxonomy recognizes six and BirdLife International's Handbook of the Birds of the World (HBW) recognizes eight. However, the IOC, Clements, and HBW do not appear to have fully accepted that treatment, as their linear sequences of species (which reflect relationships) insert the Chiribiquete emerald (C. olivaresi) between the two. by hawking from a perch.