The anthus is a small bird that feeds on grass. Since horses also feed on grass, they hate the anthus bird for stealing their food. In revenge for this hatred, the bird imitates the neighing of the horse in mockery. The bird is very fertile, producing a dozen eggs at at time.

Thomas of Cantimpré, in his Liber de natura rerum, misidentified the anthus (from Aristotle, where this story originates) as the achantis, some kind of finch, and this error was copied faithfully by later encyclopedists.