1) Feather 2) Plumage 3) Plume 4) The shaft of such a feather 
second shaft coming out of the quill of a feather
• (n.) The hypoptilum.
(from the article `bird`) ...are often plumaceous—i.e., lacking in hamuli and remaining free of each other. In many birds each contour feather on the body (but rarely on the ...
Aft'er·shaft` noun (Zoology) The hypoptilum. 
[n] - a supplementary feather (usually small) on the underside of the base of the shaft of some feathers in some birds
noun a supplementary feather (usually small) on the underside of the base of the shaft of some feathers in some birds
a supplementary feather, usually small, arising from the underside of the base of the shafts of certain feathers in many birds. · the shaft of such a feather.