quetzalhuitzilin.

QUETZAL-HUĪTZIL-IN, literally, “hummingbird of precious plumage,” Garnet-throated Hummingbird (Lamprolaima rhami) [FC: 24 Quetzalhuyjtzilin] “Its throat is chili-red, its wing-bend ruddy. Its breast is green. Its wings and its tail [feathers] resemble quetzal feathers.” Martin del Campo identified this as the Broad-tailed Hummingbird. However, that species does not show a green breast nor ruddy wing-bend. The Garnet-throated Hummingbird is a better match.
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 11 – Earthly Things, no. 14, Part XII, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1963); Rafael Martín del Campo, “Ensayo de interpretación del Libro Undecimo de la Historia General de las Cosas de Nueva España de Fray Bernardino de Sahagún – 11 Las Aves (1),” Anales del Instituto de Biología Tomo XI, Núm. 1 (México, D.F., 1940); and, with quotation selections, synthesis, and analysis here also appearing in E. S. Hunn, "The Aztec Fascination with Birds: Deciphering Sixteenth-Century Sources," unpublished manuscript, 2022, cited here with permission.

Eugene Hunn says this "is no doubt 'Quetzal hummingbird,' as in the [Florentine] Codex, which most likely references a color scheme reminiscent of that of the Resplendent Quetzal, brilliant blue-green, maybe combined with red. He illustrated this twice, so the name might well have referred to more than one species (personal communication, 21 April 2024). Chris Carlson brought this example to our attention. The orthography for this bird name has been normalized from the way it appears in Franciscus Hernández, "Historiae animalivm et mineralivm Novae Hispaniae” (https://gdz.sub.uni-goettingen.de/id/PPN473544997).