With a downward thrust of its wings, a seagull launches itself skyward. Once aloft, it wheels and turns, rising effortlessly on the wind. Making only tiny adjustments to the angle of its wings and tail, the bird hangs nearly motionless in the air. What enables it to perform those functions with such grace and perfection? To a great extent, its feathers.
Birds are the only animals today that grow feathers. Most birds have different kinds of feathers. The most visible are the overlapping contour feathers, which give birds their smooth, aerodynamic shape. Contour feathers include the wing and tail feathers, which are vital to flight. A hummingbird may have fewer than 1,000 such feathers, and a swan more than 25,000.
Feathers are a marvel of design. The central shaft, called the RACHIS, is flexible and remarkably strong. Extending out from it are rows of interlocking BARBS that form the smooth VANE of the feather. The barbs attach to one another by means of several hundred tiny BARBULES, which hook onto neighboring BARBULES, forming a kind of zipper. When BARBULES unzip, the bird simply zips them back together by preening itself. You can do the same by drawing a frayed feather gently between your fingers.
Wing flight feathers in particular are asymmetrical –the vane is narrower on the leading edge than on the trailing edge. This classic airfoil design enables each flight feather to act like a tiny wing in itself. Also, if you look closely at a major flight feather, you will see a groove running along the underside of the rachis. This simple design element strengthens the shaft, allowing it to bend and twist without buckling.
FEATHERS HAVE MANY FUNCTIONS
Distributed among the contour feathers of many birds are long, thin feathers called FILOPLUMES, as well as POWDER FEATHHERS. It is thought that sensors at the roots of the filoplumes alert the bird to any disturbance of its outer feathers and may even help it to judge its air speed. The barbs of powder feathers –the only feathers that grow continuously and are never molted –break down into a fine powder that is thought to help waterproof the bird’s plumage.
Besides their other functions, feathers protect birds from heat, cold, and ultraviolet light. Sea ducks, for example, seem to thrive despite bitterly cold ocean winds. How? Under their nearly impenetrable coat of contour feathers lies a dense layer of soft, fluffy feathers called DOWN, which may be up to 1.7 centimeters thick and cover most of the duck’s body. Natural down is so efficient yet devised equals it.
Feathers eventually wear out, so birds replace them by molting –shedding old feathers and growing new ones. Most birds molt their wing and tail feathers in a predictable, balanced order so that they always retain their ability to fly.
A LITTLE TOO PERFECT
Safe airplanes are the product of painstaking design, engineering, and craftsmanship. What about birds and feathers? In the absence of fossil evidence, controversy rages among evolutionists over how feathers originated.
One evolutionary biologist, who organized a symposium on feather evolution, confessed: “I never dreamed that any scientific matter could possibly generate such bad personal behavior and such bitterness.” If feathers clearly evolved, why should discussions of the process become so vitriolic?
Feathers are little too perfect, that is the problem. Feathers give no indication that they ever needed improvement. In fact, the “earliest known fossil feather is so modern-looking as to be indistinguishable from the feathers birds flying today. The fossil feather is from archaeopteryx, an extinct creature sometimes presented as a “missing link” in the line of descent to modern birds. Most paleontologists, however, no longer consider it an ancestor of modern birds. Yet, evolutionary theory teaches that feathers must be the result of gradual, cumulative change in earlier skin outgrowths. Moreover, feathers could not have evolved without some plausible adaptive value in all of the intermediate steps.
To put it simply, even in theory, evolution could not produce a feather unless each step in a long series of random, inheritable changes in feather structure significantly improved the animal’s chances for survival. Even many evolutionists find it a stretch of the imagination that something as complex and functionally perfect as a feather could arise in such a way.
Further, if feathers developed progressively over a long period of time, the fossil record should contain intermediate forms. But none have ever been found, only traces of fully formed feathers. Unfortunately for evolutionary theory, feathers are very complicated.
AVIAN FLIGHT DEMAND MORE THAN FEATHERS
The perfection of feathers is just one problem for evolutionists, for practically every part of a bird is designed for flight. For instance, a bird has light, hollow bones as well as an unusually efficient respiratory system and specialized muscles to flap and control its wings. It even has a number of muscles to control the position of individual feathers.
And it has nerves that connect each muscle to the bird’s tiny but amazing brain, which is preprogrammed to control all these systems simultaneously, automatically, and precisely. Yes, this whole, incredibly complex package is necessary for flight, not just the feathers.
Keep in mind, too, that every bird develops from a tiny cell that contains the complete instructions for its growth and instincts, so that one day it can take to the sky.
A BIRD’S-EYE VIEW
The vivid and often iridescent colors of feathers fascinate humans. But feathers may look even more interesting to other birds. Some birds have 4 types of color-detecting cones in their eyes. While humans have only three. This extra visual equipment enables birds to perceive ultraviolet light, which is invisible to humans. Male and female birds of some species look alike to humans, but the male’s feather reflect ultraviolet light differently from the females. The birds can see the difference, which may help them to identify potential mates.