Large toucans (Ramphastos) are divided into two groups of species, the "croakers" and the "yelpers," based on the quality of their characteristic loud vocalizations. The Channel-billed Toucan is the most widespread species of "croaker." It occurs northwestern Colombia east across most of northern and central South America, including all of Amazonia; and also is found in the Atlantic Forests of southeastern Brazil. The general behavior of this species is typical of large toucans. It forages in the upper levels of humid lowland forest, consuming a varied diet of fruit, large arthropods, and small vertebrates (such as nestlings and eggs of smaller birds, frogs, and roosting bats). They usually travel solitarily or in pairs, but may form small flocks, and also join aggregations of other species (including other species of toucans) in fruiting trees. Across most of its range, the Channel-billed Toucan overlaps with a larger species in the "yelping" group, the White-throated Toucan (Ramphastos tucanus). In eastern South America, the two species can be distinguished by the color of the breast and of the bill, but in western Amazonia, the pattern of the bill and plumage is amazingily similar in both species. Aside from the distinctly different voices of the two, the bill of the Channel-billed Toucan is relatively smaller than is the bill of the larger species. The Channel-billed Toucan is geographically variable, with four subspecies that differ primarily in the color of the bill, of the bare skin on the face, and of the breast and uppertail coverts. Each of these subspecies formerly was classified as a separate species, but they intergrade with one another where their ranges meet. All of the subspecies share a peculiar longitudinal groove or "channel" along the maxilla.