Colima Pygmy-Owl is a newly-recognized species. Previously these populations were classified as subspecies of Least Pygmy-Owl (Glaucidium minutissimum), although now the name Least Pygmy-Owl is applied only to the birds in eastern South America. Colima Pygmy-Owl occurs on the west slope of Mexico, from Sonora south to Oaxaca. This species overlaps geographically with the slightly larger Ferruginous Pygmy-Owl (Glaucidium brasilianum), but Colima Pygmy-Owl can be distinguished by its shorter tail, spotted crown, and different song. This species occurs in thorn forest, semi-deciduous forests, and coffee plantations, and locally also in pine-oak forests. The song of Colima Pygmy-Owl is a short series of hollow hooting notes. As is typical of Glaucidium, Colima Pygmy-Owl is partially diurnal and hunts for invertebrates and small vertebrates, but there is very little information available about its biology.