yohualcuauhtli.

YOHUAL-CUĀUH-TLI, literally, “nocturnal eagle/hawk,” perhaps Northern Potoo (Nyctibius jamaicensis) [FC: 40 Iooalquauhtli]: “It is the same as the white eagle. It is called “nocturnal eagle” because it appears nowhere much by day, but at night it eats, it preys on [its victims].” Another puzzle. It most likely refers to some type of large owl (Strigiformes) or large nightjar (Caprimulgiformes). Perhaps this is the Northern Potoo, though that is a species more typical of tropical lowland swamps.
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); 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analysis here also appearing in E. S. Hunn, "The Aztec Fascination with Birds: Deciphering Sixteenth-Century Sources," unpublished manuscript, 2022, cited here with permission.

The Florentine Codex (Book 11, folio 42v) has a painting of this bird.
Available at Digital Florentine Codex/Códice Florentino Digital, edited by Kim N. Richter and Alicia Maria Houtrouw, "Book 11: Earthly Things", fol. 42v, Getty Research Institute, 2023. https://florentinecodex.getty.edu/en/book/11/folio/42v/images/a453ddd6-1... Accessed 17 October 2025.