Only Birds Have Feathers

03/03/2020 20:12

Only Birds Have Feathers
Feathers are the ultimate characteristic of birds. No other
(living) animals have them. The qualifier is required because
feathers have now been found in fossil imprints of some
dinosaurs and related reptiles.

Like hair on mammals and scales on reptiles, feathers are part
of the skin. All are largely composed of keratin, which is also
the main ingredient of human nails, animal claws, and the
scales on the legs and feet of birds.
Feathers are remarkable structures, both very strong and very light. They’re subject to long flights and are
bent and twisted, yet they are rarely damaged. Abrasion causes their tips and edges to wear, but this is natural
and remedied periodically through molt. Melanins are common pigments that can make feathers black. Dark
feathers containing melanins are more resistant to damage than other feathers. This is why the outer wing
feathers of many birds with white wings, such as gulls and snow geese, have black tips.
Birds have several different feather types that vary in shape, structure, and function. The most familiar is
the contour feather. It consists of a central shaft and countless barbs that protrude from either side, forming
vanes.
Vanes of contour feathers must be rigid and flexible at the same time. A magnifying glass reveals that each
barb has smaller barbs, called barbules, projecting from either side, toward the adjacent barbs. The barbules
on one side of the barb are straight, while those on the other are hooked. If barbs separate and the vane split,
the bird can repair it by preening. Running the barbs through its bill reconnects the hooks like a zipper.
Strong, rigid vanes are especially important for flight. The trailing, inner wing feathers, the secondaries,
provide lift, while the trailing, outer wing feathers, the primaries, provide thrust. Most species have large tail
feathers. They function like a rudder when flying and like brakes when landing.
Smaller contour feathers cover the body and leading edges of the wings. On the wings, the feathers help form
the airfoil shape that is necessary for flight. On the body, they contribute color, which is important in
courtship and for camouflage, and they form a sleek outer covering, providing an aerodynamic tear-drop
shape that assists flight. From songbirds to swans, the neck is narrow and the breast muscles are massive.
Where the body parts meet, contour feathers create a gradual slope.
Another type, down feathers lie under the body’s contour feathers, forming a mass of feathers that trap air,
forming an excellent layer of insulation.
Other types are quite specialized. They are associated with sensory receptors in the skin, and are thought to
provide information about wind, air pressure, and feather movements that birds use to maintain efficient
flight.

Feathers are highly engineered structures that perform essential functions. Lightweight and strong, they allow
birds to be amazing creatures. Source: Birdwatchingdaily.com