The genus Empidonax is a group of small insect-eating passerine birds in the tyrant flycatcher family, the Tyrannidae. The genus name Empidonax is from Ancient Greek empis, "gnat", and anax, "master". Most of these birds are very similar in plumage: olive on the upper parts with light underparts, eye rings and wing bars. In the nesting season they may be distinguished by range, habitat and call; in other situations, particularly on migration and in winter, it may not be possible to be sure of specific identification. Empidonax flycatchers often flick their wings and tails rapidly.