Feathers exemplify the wonders of intelligent engineering, and indicate incredible design. Feathers are a unique integument [natural outer covering] that belongs only to birds, and are described by Richard Prum as “the most complex epidermal appendages found in animals” (1999, p. 291). Consider the feather’s state-of-the-art design. Each feather has a shaft that runs along the center. The fluffy strands that extend from the shaft are called vanes. Each vane is composed of even smaller thread-like strands, called barbs. These various barbs allow the feather to achieve lift. But the structure is even more streamlined. On either side of the barb are microscopic barbules. One side has barbules comprised of ridges, whereas the other side is composed of hooks. The hooked barbules thus attach to the ridges of the adjacent barbules, forming a sort of natural Velcro®. Actually, the feather has a better design than Velcro, because the ridges allow the barbs to slide, keeping the surface intact, and yet allowing it the flexibility required for flight. Thus, it can be said that birds of a feather flock together, and feathers of a bird lock together.
-Matthew Vanhorn
Prum, Richard O. (1999) “Development and Evolutionary Origin of Feathers,” Journal of Experimental Zoology (Molecular, Developmental, Evolution), 285:291-306.