Shafts, Vanes and Barbs: The Science of Feathers

How Feathers Work

1Birds are the only animals alive today that have feathers. A feather may look delicate, but it is made of keratin, a tough material that is also found in your hair and fingernails. Feathers do many jobs. They help birds fly, keep them warm and dry, and even help them attract mates.

2The feathers that cover the outside of a bird are called contour feathers. They overlap like shingles on a roof and give the bird a smooth, streamlined shape. A streamlined body has smooth edges and a sleek shape, so air flows easily around it. The long, stiff feathers on the wings and tail are called flight feathers. They help a bird lift off, steer and land.

3If you look closely at a contour feather, you will see a stiff tube down the middle. This is the shaft. On both sides of the shaft is the vane, the flat, flexible part of the feather. Unlike the stiff shaft, the vane can bend easily. The vane is made of many thin branches called barbs. Each barb has even tinier branches called barbules, and many barbules have microscopic hooks that you could only see with a microscope. The hooks grab onto each other like the teeth of a zipper, holding the vane together so it can push against the air.

4Under the contour feathers lies a layer of down. Down feathers are short and fluffy, and their barbs do not hook together. Instead, they puff out and trap pockets of air close to the bird's skin. This trapped air acts as insulation, a barrier that slows the loss of body heat. That is why many birds look puffed up on a frosty morning.

5Feathers need care to keep working. Birds spend time every day preening. To preen, a bird runs each feather through its beak, cleaning it and zipping split barbs back together. Many birds also spread oil from a small gland near the tail, which helps keep their feathers waterproof. Even with good care, feathers wear out. So birds molt, shedding old, worn feathers and growing new ones in their place.