amanacoche.

AMANACOCHE, Bufflehead (Bucephala albeola) [FC: 35-36 Amanacoche] “It is called amanacoche because of its white feathers placed on both sides of its head. It is the size of the [Green-winged Teal]….” I agree with Martin del Campo that this is certainly the Bufflehead. See also CANAUH-TLI “duck.”
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analysis here also appearing in E. S. Hunn, "The Aztec Fascination with Birds: Deciphering Sixteenth-Century Sources," unpublished manuscript, 2022, cited here with permission.

auh in inechichihual tezcatzoncatl, aztatzone, yacametze, amanacoche = "and the array of tezcatzoncatl [was thus]: he had the white heron feather headdress; he had the crescent-shaped nose ornament, the ear plug of paper. (Florentine Codex, b.1 f.3 p.51)
R. Joe Campbell, Linguist List posting, August 28, 2000. http://listserv.linguistlist.org/pipermail/nahuat-l/2000-August/001203.html