How do Birds Fly, Soar?
From ancient times, we humans saw birds flying.
In the late 1400s, Leonardo da Vinci created a wing-flapping contraption called an orni-thopter (from the Greek word orni-thos for bird and pteron for wing).
He thought flying was simply a mat-ter of flapping wings up and down. The ornithopter did not work because he did not understand how bird wings must generate lift and thrust to fly.
Birds have very special features (like beaks, feathers, and wings).
Birds have feathers and bones adapted for flight.
With these adaptations, they can take off, hover, soar, glide, dive, and land in amazing ways.
One of the things that really helps birds to be able to fly is that they are lightweight.
When a bird or airplane is moving through the air, the air splits its path at the front edge of the wing and meets again at the back of the wing.
Because the top of the wing is curved, the distance from the front of the wing to the back of the wing is shorter for air passing under the wing.
Air passing over the wing top moves more quickly than air under the bottom.
The fast-moving air atop the wing creates less pressure than air
Underneath the wing.
The higher air pressure under the wing lifts the bird upward.
At the same time, wing flapping acts like a propeller to move, or thrust, the bird forward.
Swiss mathematician Daniel Bernoulli first explained lift using an equation. This important discovery, known as Bernoulli’s Principle, helped people learn how to achieve flight.
Birds make flying look easy.
They seem to simply flap their wings and fly. Certain adaptations make birds perfectly suited to fly in certain ways and places.
They have specialized feathers and use 50 different muscles that allow complicated movements.
Leaping. A bank swallow drops from its nesting cavity on the side of a cliff or steep bank. Gravity pulls on the swallow, helping it reach the critical speed at which its spread wings generate enough lift to become airborne. Herons, egrets, hawks, and other birds leap upward as they push
their wings downward to lift off.
Beating Wings. Many songbirds don’t have very strong legs. Neither do grouse, pheasants, and puddle ducks, such as mal-lards and teal. These birds rise from the ground or water with a powerful down-ward thrust of their wings. Like airplanes accelerating down a runway, many birds face the wind and run and flap their wings across a stretch of land or water to gain enough speed to lift off. To take off, sandhill cranes run into the wind across a field or grassland. A common loon has small wings compared with its body size and weight. To get airborne, a loon must run a long way across the surface of the water while flapping its wings fast.
Hovering. Hummingbirds never run, walk, or hop. They use their feet only
for perching. Minnesota’s ruby-throated hummingbird takes off from its perch by lifting its feet and beating its wings to hov-er up and away. Even if a hummingbird wants to move only two inches to the left on its perch, it must let go, hover up and to the left, then descend and perch again
Tail. When a bird raises its tail, the tail helps the bird climb high-er in the sky. To dive, a bird points its tail toward the ground.
The tail helps the bird slow down or stop flying and turn
right or left. When a hummingbird approaches a flower, it low-ers and spreads its tail feathers, so more air drags against the tail. This drag (wind resistance) helps the bird slow down and hover or stop. A common tern spreads its forked tail to slow its forward movement and stay stable while hovering on the wind as it looks for a fish below. A tern can also fold its tail straight back, so it is more streamlined and creates less drag during its
long migratory flights between North and South America.
Flight Style and Birds –
Turkey vulture (Long and broad wing for soaring)
Common nighthawk (Long, angular, and pointed wing for high speed)
Greater prairie chicken (short, broad, and cupped wing for quick takeoffs)
Indigo bunting (short and broad wing for quick takeoffs and flying long distances)
Hummingbird (long, slender, and straight oarlike wing for maneuverability)
Soaring and Gliding. Using its long, broad wings, a turkey vulture can soar for hours in search of carrion, dead animals. A turkey vulture holds its wings at an up-ward angle, like a shallow letter V. This shape helps the bird stay stable in the air. If the wind tilts a vulture to one side, lift increases under the lower wing because it is extended horizontally a longer distance
than the other wing. The lift brings the bird back to a horizontal position. When the Wright brothers were designing their first successful airplane, they studied soaring turkey vultures. Many airplanes have wings with a gentle upward angle to provide stable flight.
Pelicans, hawks, ospreys, and geese have long, broad wings too. Like turkey
vultures, these birds fly with their pri-mary feathers spread out like fingers on an open hand. These fingerlike wingtips give birds extra lift because each primary feather generates its own lift. Long pri-maries also give a bird plenty of thrust in forward flight and in diving for prey.
Skydiving. Some birds, such as swallows and falcons, have long, angular wings with pointed tips. Pointed wingtips have less drag and allow a bird to perform dramatic aerial maneuvers in order to catch bugs or other prey on the wing. With its long, sleek, angular wings, a peregrine falcon can reach speeds of nearly 200 miles per hour as it dives toward other birds in flight.
Short and Fast. Birds such as pheas-ants, turkey, and grouse have short, broad wings that allow them to fly very fast over short distances. The wings are shaped like an upside-down saucer. This curved de-sign traps more air underneath the wings for a quick lift and noisy getaway from a
fox, coyote, bobcat, or other predator. Up, Down, Around. Rather than flap-ping, a hummingbird moves its straight, slender wings like the oars of a rowboat—but much faster. A ruby-throated hum-mingbird can make more than 50 wing-beats a second! A hummingbird cannot glide or soar, but it can flip its wings up-side down at the shoulder joint to gen-erate lift on both the forward and the backward strokes. By changing wing po-sition, a hummingbird can fly up, down, forward, backward, and upside down. It
is the only bird able to fly backward.
Coming for landing –
Landing is tricky—for birds (and airplane pilots). Different bird species have different methods of landing.
When a bird or airplane comes in for a landing, it must raise its body or nose upward to slow down. When a Canada goose comes in for a landing, it
raises its body slightly, spreads its tail to create drag, and spreads out its wings to slow down. If a bird in the air slows down too much, it will lose all lift. Without lift, the bird, like an airplane, would “stall” and tumble from the sky. Geese and other birds use a cluster of feathers called the alula to help them land without stalling. Sticking out the thumblike alula forces air over the top of the wing, which helps maintain lift as it slows down to land.
Touch Down on Water. Geese, mallards, and many other birds circle into the wind to main-tain lift as they slow down to land. Pilots do the same thing when landing airplanes.
As a mallard approaches landing, it points its body upward and drops its feet. Next it raises its alulas and begins flapping its wings in a nearly up-right body position. With wings held upright, the secondary feathers no longer provide lift but the flapping primary feathers give just enough lift for
the bird to hover down slowly like a helicopter.
A trumpeter swan needs more room to land than a mallard does. It raises its head and body and extends its feet forward as it glides in for a landing.
When its large, webbed feet touch the water, the swan gracefully water-skis to a stop.
Tree Landings. Some birds, such as egrets, perch on treetops. To land there, a flying egret raises its wings and beats only its primaries back and forth above its intended perch. It keeps its wings spread and stretches out its legs. As the egret drops gently from the air, its long legs reach
out and its feet grasp a branch.Songbirds use a slightly different technique
to land on a perch. When a bird such as a robin comes in for a landing, it raises its body and wings into a nearly upright position to slow down. With
feet outstretched, the robin has enough momen-tum to keep moving forward until its feet touch and grasp the perch.
(Click image to enlarge)[ SOURCE: Carrington College Veterinary Assistant Program
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Wednesday, September 19, 2012
Tags - Birds Fly
19 September 2012
How do Birds Fly, Soar?