Source : Webster's Revised Unabridged Dictionary (1913)

Plumage \Plum"age\, n. [F., from plume a feather.] (Zo["o]l.)
   The entire clothing of a bird.

   Note: It consist of the contour feathers, or the ordinary
         feathers covering the head, neck, and body; the tail
         feathers, with their upper and lower coverts; the wing
         feathers, including primaries, secondaries, and
         tertiaries, with their coverts; and the down which lies
         beneath the contour feathers. See Illust. under {Bird}.

Source : WordNet®

plumage
     n : the light horny waterproof structure forming the external
         covering of birds [syn: {feather}, {plume}]