The Wonder of Birds

“A bird is to me as wonderful as the stars,” said a famous ornithologist. To lean something about a bird is to make acquaintance with some of nature’s most breath taking miracles. In making of a bird, every step seems to have been taken with a single thought in mind: the thought of flight. Here was to be a creature that would be a ‘grace for the sky’. Here was to be lightness, arrowy strength, a sight to lift man’s spirit as if on wings itself. A bird has a small brain because it needs extraordinary eyesight for flying. Because we see only a small part of a bird’s eye, we are not likely to realise what a large organ it is. A bird’s eyes are actually so big that there is barely room in its skull for them. Many hawks and owls have eyeballs bigger than yours and mind. Therefore, these immense eyes make a bird’s brain, by comparison, seem relatively insignificant organ. In many birds, the eyes weigh more that the brain. An owl scans the dark woods with eyes ten times as sensitive to faint light as ours. A hawk, perched on the top of a tall tree, may be able to see small creatures nearly a mile away. Ruskin was not far from the truth when he spoke of a bird as ‘but a drift of the air brought into shape by plumes’. A bird inhales more air than is needed just to fill its lungs. This is because a bird’s lungs connect with as many as nine additional air sacs. Unlike the bone of a mammal, a bird bone is hollow, filled with a spongy network that can hold air. As a bird breathes, its body seems to be flooded with air. Even the skull of a bird is designed with flight in mind. Skull bones are very light in weight. To lighten the living flying-machine still further, nature took away birds teeth – for teeth need heavy jaws and muscles. For lightness aft, a bird’s tail feathers are all carried on one short bone. Feathers are the strongest structures for their size and weight known in nature. A feather may seem to be only a central stem with projections on either side. It is much more. Every projection (called a vane) from the central stem is made up of a number of parallel rods, the barbs. A bard is itself a complete miniature feather with extremely fine side-projections. These are called barbules. Look still more closely with a lens and you will see that on these barbules are tinier barbicels. And on these are even smaller hooklets. The hooklets, barbicels and barbules are all interwoven to make the whole vane. Barbules and barbicels on a single feather may number several thousands. The streamlined body of the bird is a perfect machine for flight. Its framework is the most rigid in the animal world. The vertebrae of its backbone are joined to make an extremely strong support for the other parts of its body. Its backbone, ribs and breastbone form a kind of cage of great strength. Down the middle of the backbone is a ridge to which are attached the great muscles that work the bird’s wings. In many birds, these muscles weigh more than a quarter of the bird’s whole weight. As a bird beats its wings on the downstroke, it may seem to be pushing itself forward as if rowing through the air. High-speed cameras show that it is not doing stroke, each wing moves forward. The inner half is held almost rigid, its front edge slightly sloped like a plane wing, its upper surface arched by a curve of feathers. The outer half of the wing moves separately. It is set in motion by the bird’s wrist, located about half-way along the wing’s length. During the beating of the wings, the feathers at the bird’s wing-tips flare out almost at right angles to the wing and become propellers. The inner half of the wing, curved and tilted, is meanwhile the plane wing providing steady lift. When it is landing and taking off, the bird avoids accidents by means of special feathers at the front edge of its wrist. It raises these to make a slot between them and its main wing. In flight, a bird’s actions can be almost unbelievable. A sparrow-hawk, flying at top speed, saves itself from crashing into something that may suddenly appear in its path. It performs a perfect side-swerve. A golden eagle, swooping down at a speed of more than a hundred miles an hour, brakes with superb skill. By spreading out its wings and tail, it comes to a dead halt in a space of twenty feet. A bird cushions its landing with its legs, which consist of three single rigid bones with joints that work in opposite directions. This is probably the most effective shock-absorbing mechanism in nature. Birds are so perfectly designed for flight that they can cover distances nearly beyond belief. This may lead us to wonder how birds can find their way through the track-less skies, often at night. How wonderful birds really are.