What makes a bird streamlined

The secondaries, usually numbering about six on a small bird, are for lift. They are shorter and fatter than the primaries and the shaft runs up the middle of the feather.

Since airflow is pushed under the secondaries when the wings flap downward, lift is created, enabling the bird to fly upward. Next to the secondaries on the inside are the tertial feathers, which cover the space between the wing and the body. Small birds usually have three tertials. When birds spread their wings, they look large, it is because these 20 or so large flight feathers spread out widely. When birds fold in their wings, the flight feathers overlap each other and are positioned compactly.

Birds use their tail feathers to slow down or change direction in the air. They generally have 12 tail feathers, which often resemble the shape of secondary feathers in the wing.

The difference is that the shaft of tail feathers is usually straight. The shaft of flight feathers in the wing curves slightly in the direction of movement forward or upward. Even if you attached wings to yourself with the hope of flying, you unfortunately would not be able to. That is because the secret to how birds fly is not only in their feathers but also in their body.

Firstly, there are the muscles. The muscles in the chest required for a bird to flap its wings are very well developed. In some birds, the muscles in the chest alone account for more than one quarter of its body weight. The proportion in humans is said to be one one-hundredth. And, their bodies are lightweight; the Japanese White-eye, which is smaller than a sparrow, weighs a mere 10 grams the weight of several postcards. The bones of birds are hollow inside like a tunnel, their intestines are short, and they digest food as soon as possible and expel the waste.

Since birds do not have a bladder to keep urine, liquid is expelled together with feces right away. They use their lightweight bill to eat, not a heavy jaw or teeth. Even birds that look large when they spread their wings are much lighter than they look. When you watch gulls near the seaside or pigeons in the park, you will notice that birds sit or stand facing into a strong wind the direction the wind is coming from.

The reason for this is that a bird's feathers all grow in the same direction. Bird feathers provide a streamlined coat fitted neatly along the body from the bill back toward the tail. If they faced with the wind the direction the wind is blowing , their feathers might all stand up on end and get messed up, right? This streamlined shape, also used for high-speed rail cars, allows the oncoming wind to pass around it easily. Normally, the faster you move, the more difficult it is to advance because of drag caused by the air, but with a streamlined shape there is minimal drag, enabling smooth forward movement.

Soaring flight is a special kind of glide in which the bird flies in a rising air current called a thermal. Because the air is rising, the bird can maintain its height relative to the ground. The albatross uses this type of soaring to support its multi-year voyages at sea. This propels them forward. The entire wingspan has to be at the right angle of attack, which means the wings have to twist and do so automatically with each downward stroke to keep aligned with the direction of travel.

The air is deflected downwards and also to the rear. The bird reduces its angle of attack and partially folds its wings on the upward stroke so that it passes through the air with the least possible resistance. The inner part of the wing has very little movement and can provide lift in a similar way to gliding. Birds obtain thrust by using their strong muscles and flapping their wings. Some birds may use gravity for example, jumping from a tree to give them forward thrust for flight.

Others may use a running take-off from the ground. News story about the robo-gull — a man-made bird that flies using remote control. This article includes video of the robo-gull. According to conventional wisdom, because the upper surface is longer than the lower surface, air flowing over the top has to travel faster than the air underneath. So how is lift created? When the air moving over the top of the wing passes over the trailing edge, it is deflected downward downwash , below horizontal.

The greatest amount of lift is created when air striking the leading edge of the wing is deflected upward, pulling air from above the wing with it. The action leaves a large volume of reduced pressure on the top of the wing, which generates a large amount of lift. The value of a teardrop-shaped wing is that it creates lift at a smaller angle of attack that is, the angle between the wing and horizontal than a wing shape that is flatter.

As diverse as the birds of the world are, the similarities in structure and function are profound. Certainly, one of the most prominent is the teardrop shape. It unites all of the flying and swimming birds into the amazing avian assemblage we enjoy today. Originally Published May 15, Read our newsletter! Sign up for our free e-newsletter to receive news, photos of birds, attracting and ID tips, and more delivered to your inbox. Colleagues and former students at Hope College share memories of Eldon Greij involving birds, road trips, tacos, fish fries, and more.

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