The Collaborative International Dictionary of English v.0.48:

hummingbird \hummingbird\, humming bird \humming bird\n.
   (Zool.),
   any bird of the family Trochilid[ae], of which over one
   hundred genera are known, including about four hundred
   species. They are found only in America and are most abundant
   in the tropics. They are mostly of very small size with long
   slender bills adapted to sucking nectar from flowers, and are
   noted for the very brilliant iridescent colors of their
   plumage and their peculiar habit of hovering about flowers
   while vibrating their wings very rapidly with a humming
   noise; the wings are specialized for hovering flight, but
   they can also dart forward and fly quite rapidly. They feed
   both upon the nectar of flowers and upon small insects. The
   common humming bird or ruby-throat of the Eastern United
   States is Trochilus colubris. Several other species are
   found in the Western United States. See Calliope, and
   Ruby-throat.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rubythroat \Ru"by*throat`\, n. (Zool.)
   Any one of numerous species of humming birds belonging to
   Trochilus, Calypte, Stellula, and allies, in which the
   male has on the throat a brilliant patch of red feathers
   having metallic reflections; esp., the common humming bird of
   the Eastern United States (Trochilus colubris).
   [1913 Webster]