Birdology: Adventures with a Pack of Hens, a Peck of Pigeons, Cantankerous Crows, Fierce Falcons, Hip Hop Parrots, Baby Hummingbirds, and One Murderously Big Living Dinosaur

by Sy Montgomery

Feathers are among the most complex structural organs found in nature. Nothing of comparable dimension is stronger. They are made of keratin, the same as a human’s fingernails, a horse’s hooves, and a rhino’s horn—but the keratin in feathers, due to a difference in molecular structure, is even tougher. A typical bird’s feathers outweigh its skeleton. Feathers define a bird. By trapping and moving air, feathers protect the bird from cold and wet, and they enable it to fly. But each feather is, itself, largely air, with a stiff central shaft that is light and hollow and attaches, beneath the skin, to a muscle. Like each scale on a reptile, each feather on a bird can be raised or lowered as needed. The shaft divides the feather into two broad vanes on each side, which consist of parallel branches called barbs. At right angles to the barbs are interlocking branchlets called barbules. Hundreds of pairs of tiny barbules on each barb fit together like tiny strips of Velcro and give the feather its web-like quality. The barbules have small hook-like processes called barbicels. And on the barbicels of some feathers are even tinier branchlets, microscopic hamuli, which allow even more air to be trapped in the feather. When birds preen—running their beaks through their feathers, as these babies do after Brenda ruffles them—they are rezipping the Velcro of these minute connections.