aztatl.

AZTA-TL, Snowy Egret (Egretta thula) [FC: 28 Aztatl] “It is also called teoaztatl. It is white, very white…. It is long-necked, stringy, curved. The bill is pointed, long and pointed, black. The legs are very long, stringy, stilt-like, black. The tail is stubby.” I agree with Martin del Campo that this is the Snowy Egret, though the Great Egret (Egretta alba) is quite similar, but with a yellow bill.
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analysis here also appearing in E. S. Hunn, "The Aztec Fascination with Birds: Deciphering Sixteenth-Century Sources," unpublished manuscript, 2022, cited here with permission.

Naztauh, nomecaxicol. Quitoznequi: inic onechtequimacac in altepetl: ic in itlacauh oninochiuh intla niquitlacoz, intla itla ic nicouitiliz: nictzactiaz. = My heron-feather headdress, my jacket of ropes. This means: When the city gives me a responsibility I become a slave. If I hurt the city in some way, if I endanger it, I shall be put in jail.
Thelma D. Sullivan, "Nahuatl Proverbs, Conundrums, and Metaphors, Collected by Sahagún," Estudios de Cultura Náhuatl 4 (1963), 140–141.

aztatl = egret (late sixteenth-century, Tetzcoco?)
Ballads of the Lords of New Spain: The Codex Romances de los Señores de la Nueva España, transcribed and translated by John Bierhorst (Austin: University of Texas Press, 2009), 35.

auh yoan yn jquac y, tlaacopiloaia: auh ynaca oc concholotiaia, yn iqueztepol malli: yoan mecaxicolli, aztapalactontli itech pilcac = Moreover, at this same time he put up [on the point of the pole], so that it hung—having removed the [remaining] flesh—the thigh bone of the captive, and suspended with it the sleeveless knotted cord jacket and a small spray of heron feathers. (16th century, Mexico City)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 2—The Ceremonies, No. 14, Part III, 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, 1951), 57.