Bird feathers are simply beautiful, but they are the most complex structure found among vertebrates. There are 5 parts of a contour feather, the vane (the whole side of a feather), the rachis (like a stem, runs down the center of a feather), the barb (each strand making the vane), the afterfeather (the fluffy barbs resembling a down feather) & the calamus (hollow shaft at the base). They aid in flight, insulation and waterproofing. They can be used for their nests and some digest them for food