Look at a bird feather close up sometime. It is really an amazing part of a bird's anatomy, made to serve many functions. The image shown at right in Figure 1 is that of a contour feather, the largest of the feathers you'll find on a bird. It is labeled with its basic parts to help you understand how complex it really is.
Commonly called the quill, it is the smooth, non-colored part of the feather shaft, which extends under the skin.
The portion of the central shaft that rises above the skin. It is the base from which the barbs extend.
The part of the feather that has barbs.
Set of fibers, which come off the rachis at a 45-degree angle (see Figure 2).
Very small fibers found on the barb. Barbules from one barb cross those of the next at a 90-degree angle (see Figure 2).
Barbules have these, to hook the barbules together, like a zipper, forming a tight, smooth surface.
Some feathers have a small growth at the base of the vane, which have barbs but no hooks.