Globio

Feathers

Birds have them, and so did some species of extinct dinosaurs. They’re feathers. They come in different shapes and sizes, all colors, and enable birds to fly. In much the same way hair protects and warms mammals, feathers work for birds. But they also do much more.

How Feathers Evolved

You have to go back more than 150 million years to find the beginnings of feather evolution. The earliest known feathered dinosaur had small, hollow fibers called protofeathers covering its body. The fibers may have helped keep the dino warm. This dinosaur, Sinosauropterix (sigh-no-sore-OP-ter-icks], was found in China’s Liaoning Province, along with the fossils of many feathered dinosaurs. Scientists believe that feathers evolved in stages, possibly from scales. They know that feathers evolved before flight, because many feathered dinosaurs could not fly.

Early feathers seem to have been used for protection and warmth. Dinosaurs later developed more modern feathers, which may have helped certain species glide from tree to tree. Non-avian dinosaurs became extinct about 65 million years ago. What happened to avian dinosaurs? They survived to become today’s birds.

How’s a Feather Put Together?

Feathers are made of keratin. That’s the same stuff that makes up human hair and fingernails, reptile scales, and shells. Keratin also forms birds’ beaks and the scales and claws on their feet.

Different Jobs for Different Feathers

Contour feathers are vaned feathers that you see covering a bird’s body. They protect the bird and help keep it warm and dry. Flight feathers are large vaned feathers of the wing and tail that are shaped to help birds fly. In between the contour feathers are semiplumes that provide both support and insulation. They appear to be a cross between a vaned feather and a down feather.

Underneath the contour feathers are down feathers. The rachis of these feathers is very small or gone altogether, and the barbs are soft and fluffy. The purpose of down feathers is to trap air between the feathers and the bird’s skin to insulate it. Some birds, such as baby chicks, are born covered in down.

Other feathers act as sensors. Filoplumes are bare except for a few barbs. They grow around contour feathers and may help birds sense the position of feathers in flight. Hairlike bristles grow around some birds’ beaks or eyes. Bristles may help birds such as swallows catch prey by funneling insects toward the mouth. They may also protect the eyes. Woodpeckers have bristles over their nostrils that help keep wood chips out. Bristles may also act like a cat’s whiskers, helping a bird feel what’s around it.

Keeping Warmth In and Water Out

Feathers are specially adapted to help birds survive. For example, a penguin’s feathers are small and tightly packed. Down near the skin traps body heat, keeping a penguin warm even while swimming in icy waters. The feathers also provide a sort of wet suit to keep the penguin dry. The outer feathers overlap, shutting out water.

Preening helps keep feathers waterproof and in good condition. Birds have a gland near the base of their tails that produces oil. Using their beaks or bills, the birds spread this oil over their feathers. The oil coats the feathers so water really does run off a duck’s back! Other birds such as pigeons and herons have powder down feathers, which grow all the time but break down at the tips. This creates a fine powder that may be used to help waterproof the bird.

It’s important for birds to keep their feathers clean and in good shape. Damaged or dirty feathers lose their ability to keep the bird warm and dry. One reason oil spills are so dangerous for birds is that the oil destroys the feathers’ waterproofing and warming abilities. It also weighs the birds down, preventing flight or swimming. When birds try to preen, they swallow the oil, which is poisonous.

Feathers for Flight

Without feathers, birds wouldn’t be able to get off the ground. But why? A bird’s flight feathers have shorter vanes on the side facing the front of the wing and longer vanes behind. The front-facing side is called the leading edge. It’s the edge that moves into the wind. A bird’s flight feathers and wing shape create an airfoil. Air moves faster over the curved top of the feathers and slower beneath them. The faster-moving air pulls at the wing, lifting it. If you look at the shape of an airplane wing, you’ll see that it’s an airfoil too. Flight feathers in birds’ tails and wings not only get them aloft, but also help them steer and come to a stop.

Males Show and Tell

Plumage – the word for a bird’s feathers – plays a big role in attracting a mate. The male peacock may be the showiest of all. When he wants to impress the ladies, he fans his long tail feathers. More than just a flashy display, the hens can judge how healthy and fit the male is by the condition of his feathers. Scientists believe that healthier birds may produce more vibrantly colored feathers. Potential mates may look for this.

Females Duck for Cover

While males’ feathers may be bright and flashy during nesting season, females tend to be drab. Mallard ducks are a good example. Aside from a bright blue patch on the wings, the two look completely different. During nesting, mallard females need to blend into their surroundings to be safe from predators. Young birds may also have feathers that help camouflage them while in the nest or on the ground before they are able to fly. Willow ptarmigans’ (TAR-mig-an) feathers change from speckled brown in spring and summer to solid white in winter. The white feathers help them blend into their snowy surroundings.

Birds are able to change their plumage through seasonal molting. Young birds will molt their juvenile plumage at least once before they look like an adult. During molting, some or all of the feathers are replaced. Molting is stressful to birds. A few species aren’t able to fly when they lose wing feathers. Birds molt completely one or two times per year.

All the Colors of the Rainbow, Plus More

From a white owl to a bright parrot, birds come in all colors. In fact, birds are able to see colors that humans can’t. How do feathers get their brilliant color? Two factors come into play.

Pigments are colors found in plants and animals. For instance, burning wood creates the black pigment you see in charcoal. Birds produce three types of pigments that give feathers color. Melanin is a black or brown pigment. When birds eat plants or plant-eating animals, they may acquire carotenoids, which are usually yellow, orange, or red. The carotenoids in the shrimp they eat are what make flamingos pink. Other pigments produce green and red feathers.

The second way feathers get their color is from special ways light works with a feather’s structure. On a ruby-throated hummingbird, the male’s throat feathers may appear dark and dull until the light hits them just right. Then the brilliant red flashes because the feathers reflect it, creating the iridescent jewel-like color that gives the bird its name. Most blue birds appear blue because of the way light reflects off their feathers.

Not Just for the Birds

Birds aren’t the only ones to find feathers useful. People used to write with quill pens made from large vaned feathers. Feathers were also used as stuffing for pillows and bedding. In the late 1800s feathers became the height of fashion. Women would sometimes wear the bodies of whole birds on hats and clothes. Feather-trimmed hats were so popular that hunters killed millions of birds—especially egrets and herons—for the trade. In the 1900s, passage of laws limiting hunting and the influence of conservation groups such as Audubon societies helped protect birds.

To American Indians and other native peoples, feathers are important culturally and spiritually. Feathers of eagles, hawks, and crows adorned Indian headdresses, clothes, and other items. Eagle feathers are especially prized and once signified a warrior’s triumph in battle. The Kayapo people of Brazil make headdresses of macaw and stork feathers. Natives in Papua, New Guinea, use the tail feathers of birds of paradise for decoration. The use of feathers from threatened or endangered birds is illegal, but laws allow for their possession for cultural and religious reasons.  

Today people use down feathers from domesticated birds to stuff pillows, blankets, mattresses, and coats. Just as they do for birds, feathers also keep people warm and comfortable.