cohuixin.

COHUĪX-IN, Aztec Rail (Rallus tenuirostris) [FC: 34 Covixin] “It is a waterfowl. It is called couixin because when it speaks it say couix, couix, couix. It is… a little larger than a dove. Its head is quite small; its bill is chili-red, black at the end, small and cylindrical. Its back, its wings, its tail are all like quail feathers; its breast alone is tawny. Its legs are chalky, very long…. The bird rears no young here; it also comes and it also goes. It eats fish…” (34). For some reason, Martin del Campo identified this bird as the Black-bellied Plover (Pluvialis squatarola), though this shorebird is “Irregular R[are] to U[ncommon] transient and winter visitor… in interior [or Central Mexico]” (Howell & Webb). Neither do other descriptive details fit this species. It is more likely a species of rail (Rallidae) most likely the Aztec Rail.
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); Steven N. G. Howell and Sophie Webb. A Guide to the Birds of Mexico and Northern Central America (Oxford University Press, Oxford, New York, Tokyo, 1995); 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analysis here also appearing in E. S. Hunn, "The Aztec Fascination with Birds: Deciphering Sixteenth-Century Sources," unpublished manuscript, 2022, cited here with permission.