xomotl.

XOMO-TL, perhaps the Royal Tern (Thalasseus maximus) and/or Elegant Tern (Thalasseus elegans) [FC: 27 Xomotl] “It is crested, short-legged, squat. The feet are wide, black, dark, blackish. It is a water-dweller, a fish-eater.” Martin del Campo identified this bird as the Mexican Duck (Anas diazi), though he suggested that it might refer to a variety of species. The description does not fit any duck, which are probably already named as some kind of CANAUH-TLI. I suspect the bird so-named is a species of tern. The Royal Tern and the Elegant Tern are prominently crested but strictly coastal. The Caspian Tern (Hydroprogne caspia) and Forster’s Tern (Sterna forsteri) may frequent highland lakes in Central Mexico in the off-season, so more likely to have been known to the Aztec scribes, but are not crested.
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analysis here also appearing in E. S. Hunn, "The Aztec Fascination with Birds: Deciphering Sixteenth-Century Sources," unpublished manuscript, 2022, cited here with permission.