Traditionally, the bird order Apodiformes contained three living families: the swifts, Apodidae, the tree swifts, Hemiprocnidae, and the hummingbirds, Trochilidae. In the Sibley-Ahlquist taxonomy, this order is raised to a superorder Apodimorphae in which hummingbirds are separated as a new order, Trochiliformes, but this has been refuted by subsequent research. With nearly 450 species identified to date, they are the most diverse order of birds after the passerines.

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