tolcomoctli.

TOL-COMOC-TLI, onomatopoetic, American Bittern (Botaurus lentigenosus) [FC: 33 Tolcomoctli] “Also its name is atoncuepotli and ateponaztli. It is rather large, the same size as the Castilian chicken, the capon. Its head is dark yellow; its bill yellowish, small, and cylindrical, about a span in length. Its breast, its back, its tail, its wings are all dark yellow, slightly blackened; its legs, its shanks, are dark. And for this reason is it called tolcomoctli: as it sings, it resounds. For this reason is it called atoncuepotli: when it sings, it is clearly heard to explode; it is very loud. And it is called ateponaztli because it sounds from a distance like a two-toned drum, so loud it is. This [bird] always lives here in the reeds; here it raises its young….” This is the American Bittern and is most aptly named. In FC: 57, “Atoncuepotli” is contrasted with “Ateponaztli” as if they were two species, though both sound the same, “as if someone beat the two-toned drum.” However, acoyotl <Ā-COYO-TL> is the Neotropic Cormorant and atotlin <Ā-TŌTO-LIN> is the American White Pelican. It is said that all three are so-called “because [they are drowners] of men.” I believe that Ā-TEPONĀZ-TLI and Ā-TONCUEPO-TLI are synonyms for the American Bittern, as this bittern does in fact produce a sound like a TEPONĀZ-TLI, “lateral log drum” (Karttunen). See also Ā-TEPONAZ-TLI, Ā-TONCUEPO-TLI.
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); Frances Karttunen, An Analytical Dictionary of Nahuatl (University of Oklahoma, Norman, 1983); 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analysis here also appearing in E. S. Hunn, "The Aztec Fascination with Birds: Deciphering Sixteenth-Century Sources," unpublished manuscript, 2022, cited here with permission.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 has a painting of the tolcomoctli in Book 11, folio 33r.
Available at Digital Florentine Codex/Códice Florentino Digital, edited by Kim N. Richter and Alicia Maria Houtrouw, "Book 11: Earthly Things", fol. 33r, Getty Research Institute, 2023. https://florentinecodex.getty.edu/en/book/11/folio/33r/images/0 Accessed 17 October 2025.