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Home , Bird flight, Insect wing

Flight in : & – EVERYTHING YOU NEED TO KNOW!!!!

Feathers and flight A bird is designed for flight. The combination of light weight, strength and shape, as well as precision control, is largely responsible for giving their special ability for sustained flight. Every part gives maximum power with a minimum of weight. The heavier the animal, the bigger its need to be. The bigger the wings, the more muscle is needed to move them. Birds’ are essential for flight.

Birds’ feathers are light, strong and flexible Birds’ feathers are designed to be light but very strong, flexible but very tough. Although it looks like feathers grow all over a bird, they actually grow in specific areas called tracks. In between the feather tracks are down feathers. This keeps the body weight down. Feathers are made of a tough and flexible material called keratin. The spine down the middle, called the shaft, is hollow. The vanes are on the two halves of the feather. They are made of thousands of branches called barbs. Because there are many spaces between these barbs, a feather has as much air as matter.

Contour feathers The contour feathers of a bird are the outside feathers – the ones that you can see. They provide the colour and the shape of the bird. The contour feathers tend to overlap each other, much like tiles on a roof. The feathers tend to shed rain, keeping the body dry and well insulated. Each contour feather can be controlled by a set of specialised muscles, which controls the position of the feathers, allowing the bird to keep the feathers in a smooth and neat condition. The smooth and streamlined surface is achieved because the feathers’ barbs are joined together with barbules (branches on the barbs). The barbules have hooks that lock the barbs together. If the barbules are disrupted, the bird passes its bill though the feather to link them again. The contour feathers used for flight are known as remiges ( feathers) and rectrices ( feathers).

Remiges (wing flight feathers) These feathers are strong and stiff, supporting the bird during flight. They can be divided into three groups: • Primary feathers: These are the largest of the flight feathers and propel the bird through the air. They are the farthest away from the body, attached to the skin of the wing on the ‘hand’ of the bird. In most bird species, there are 10 primary feathers on each wing. If these flight feathers are damaged or lost, a bird cannot . • Secondary feathers: These run along the ‘arm’ of the wing and sustain the bird in the air, giving it . The number of secondary feathers varies with different species. Experiments have shown that, if half of the secondaries are removed, a bird will still be able to fly, but some control will be lost. • Tertiary feathers: These are on the ‘upper arm’ of the bird. They are the short, innermost flight feathers on the rear edge of a wing, close to the body of the bird. They are not as important for flight as the primary and secondary feathers.

Rectrices (tail flight feathers) The rectrices or tail flight feathers are mainly concerned with stability and control. They are used as a rudder, helping to steer and balance the bird and allow the bird to twist and turn in flight. These feathers also act as a brake for landing.

Coverts Bordering and overlaying the edges of the remiges and the rectrices are rows of feathers called coverts. These help streamline the shape of the wings and tail (minimising ) while providing the bird with insulation.

Angle of Attack: An important aspect of lift is the (defined as the angle the wing is to the oncoming air force). At a certain angle of attack the bird will and fall. This happens with planes if they try to fly up to fast- they stall. What is the critical angle of attack anyhow? This is a tricky questions because it depends a lot on airspeed. It also depends on the type of wing a bird has. For instance, certain birds that fly at low speeds, like , have different types of wings with slits in them that allow them to break up turbulence and gain lift. (Birds also have an , or a mid wing slot that allows them to fly at different speeds - similar to the flaps on an airplane wing).

THRUST: While lift is always an issue for birds, we have yet to talk about thrust, or the act of moving the bird forward. Just flapping a wing up and down isn't going to move it forward, just up. For birds, their solution comes from the unique rotation of their wings. As the wings beat, the primary flight feathers actually twist to provide thrust. This twist is partly a result of asymmetrical veining of the feathers.

Types of Wings

• High Aspect Ratio Wing: • a. Much longer than it is wide. Has lot of vertical lifting area. Not much slotting. • b. Not fast flying birds but more soaring birds • c. , or Frigate bird.

• Elliptical Wing: • a. Tends to be even pressure over most of the surface. • b. Usually found in birds that live in forests. … facilitates a subtle change in the angle of the wing. • c. Sparrows.

• High speed Wing: a. Falcons, Plovers • b. Wings that are narrow and come out to a sharp tip. These wings reduce drag. More of the wing-beat is producing forward thrust.

• High lift Wing • a. Extreme slotting in the wing-tips • b. Vultures, , etc.

How Fly: The key to a 's flight is in its wing patterns. Generally, birds flap their wings up and down. This is not the case with the hummingbird, however. The hummingbird by oscillating its wings forward and backward in a figure eight pattern very rapidly. Seventy-five percent of the bird's lift is produced during the downstroke of this wing pattern. The figure eight pattern can be likened to a swimmer doing figure eights in the water to remain afloat.

Bat flight vs. – which one is most efficient?!

Unlike and birds, which have relatively rigid wings that can move in only a few directions, a bat’s wing contains more than two dozen joints that are overlaid by a thin elastic membrane that can stretch to catch air and generate lift in many different ways [video]. This gives bats an extraordinary amount of control over the three- dimensional shape their wings take during flight, Swartz explained. “Insects can move the joint at the insect equivalent of a shoulder, but that’s the only place where they can exert force and control movement,” she said. Birds have many more joints in their wings, but it’s nothing compared to bats. “Bats are operating with the same skeleton that we have. Every joint in the human hand is there in the bat’s wing and actually a couple more,” Swartz told LiveScience. “Think about the degree of control that we have over the shape of our hands—bats are able to extend that to make fine adjustments during flight.” It was once thought that despite having so many wing joints, it was more efficient for bats to stabilize their wings and wave them up and down like relatively rigid paddles the way birds do. “What we see when we look more closely is that in fact, it’s not what they’re doing,” Swartz said in a telephone interview. “It suggests that they’re able to take advantage of this highly jointed system to make subtle adjustments to the wing shape during flight.” The other key to a bat’s efficient flight lies in its highly elastic wing. Videos from the wind tunnel tests show that a bat’s wing is mostly extended for the down stroke during straightforward flight. But because the membrane can curve and stretch much more than a bird’s wing can, bats can generate greater lift for less energy. By blowing non-toxic smoke over the bats [video] as they were flying, the researchers were also able to create a video that revealed how air flows around the creatures as they flap their wings. The data showed that during the down stroke, the air vortex—which generates much of the lift in flapping-wing flight— closely tracks the animals’ wingtips. But in the upstroke, the vortex appears to come from another location entirely, perhaps the wrist joint. The researchers think this unusual pattern helps to make bat flight more efficient and credit it to the tremendous flexibility and articulation of the wing.

Insect Flight Basics

Insect wings are driven up and down by flight muscles located in the animal's . There are two types of mechanisms, based on how the flight muscles transmit force to the wings. They are called direct and indirect flight mechanisms. In the direct flight mechanism, at least one power muscle connects to the wing…DIRECTLY! For example, a wing depressor muscle might attach to a special part of the wing near the wing base, and directly pulls the wing down when the muscle contracts. The direct flight mechanism is more primitive than the indirect mechanism, and so we find it on older insects (evolutionarily speaking), such as and . Make no mistake, however – insects with the direct flight mechanism are not inherently worse flyers than those with the more advanced indirect mechanism. In fact, dragonflies are some of the most impressive fliers out there, due in part because their direct flight mechanism allows them to independently control each of their 4 wings.

In the indirect flight mechanism, on the other hand, the flight muscles invest their energy into deforming the insect’s thorax, which in turn causes the wings to move up and down. This mechanism in particular involves a pretty complicated hinge system at the wing base, which scientists are still trying to understand. The majority of flying insects have indirect flight muscles, including and moths, , and crickets, flies and bees. The big benefit of the indirect flight mechanism is that the thorax is able to store substantial elastic energy from each half-stroke (like a spring), and return it to help propel the subsequent half-stroke, in a process that involves mechanical resonance. Such a system makes flapping flight more energy-efficient.

Wing Movement In most insects, the forewings and hindwings work together. During flight, the front and rear wings remain locked together, and both move up and down at the same time. In some insect orders, most notably the , the wings move independently during flight. As the forewing lifts, the hindwing lowers. Insect flight requires more than a simple up and down motion of the wings. The wings also move forward and back, and rotate so the leading or trailing edge of the wing is pitched up or down. These complex movements help the insect achieve lift, reduce drag, and perform acrobatic maneuvers.

How Insects Fly

When a bee zips across your garden, it blurs by at jet speed and turns on a dime like no airplane in the world. And when a fly zooms through your kitchen and sniffs a possible snack, it can stop short in midair and hover like a helicopter to check it out. If disappointed, the fly can twirl in an aerial loop-the-loop and land upside down on the ceiling. Then it takes off backward, and flies sideways out the open window. "Insects don't just stay in the air," says entomologist (scientist who studies insects) Michael Dickinson at the University of California at Berkeley. "They perform aerial maneuvers, fly up, down, and sideways, and respond to changes in wind speed and direction."

For many bugs, flying is the only way to travel, providing access to food that other creatures can't reach, and a swift escape from predators. More than 99.9 percent of the 900,000 species of insects on Earth are classified as , or winged insects. Entomologists say these invertebrates (backboneless animals) were the first creatures to fly, dating from the period about 360 million years ago.

But for centuries, scientists have puzzled over exactly how insects perform their amazing acrobatic aeronautics. Though they haven't deciphered every secret, researchers have made new discoveries-and are now applying the principles of insect flight to the designing of sophisticated new planes.

Winging It The real secret to how insects fly lies in the wings, both in their design and in how they're used. Most insects rely on two pairs of wings, which join or overlap so they work together as a single pair. Insect wings are one of nature's lightest structures, lacking bone and muscle; they're made of chitin, an extremely tough material that also composes an insect's hard outer skin. Chitin is a polysaccharide, a chemical compound that forms fibrous molecules (in which hydrogen atoms bond to produce extra strength). A network of veins also lends insect wings extra support.

Wings on insects, bats, birds, and airplanes share a similar shape, called an : they're curved on top and flat on the bottom. Air rushing over the wing has to travel farther because of the curvature, so this air moves faster than air below the wing. Since fast-moving air exerts less pressure than slow-moving air, the difference creates suction, called lift. Lift is what pulls a wing-and a plane or critter-skyward. Each downward wing flap creates more lift, propelling the creature up and forward.

Flying Flap

But the researchers found that insect flight is far more complex than previously thought. Large-bodied insects lift off by flapping their wings very rapidly: for bees and flies, about 200 times per second. Some midges and flap their wings up to 1,000 times per second! What powers such energy? Strong muscles in the midsection, or thorax. For their size, they're the most powerful muscles known in nature.

Michael Dickinson has also discovered that insect wings don't just flap up and down. On the upstroke, insect wings move differently from those of most other flying creatures-in a kind of figureeight motion. As the nears the end of a forward stroke, the wing rotates backward, twisting upside down, parallel to the ground. This rotation accelerates (speeds up) the flow of air over the wing.

This means that insect wings generate a burst of lift and speed from the upstroke as well as the downstroke-unlike the wings of birds or bats, which derive most of their flying power only from the downstroke. "Such elaborate wing movements create miniature tornadoes that send bugs soaring by sucking the wings upward.”

Buggy Helicopters Ellington's team documented wing movements of hawkmoths and the air currents they whip up. The scientists tethered a hawkmoth to the end of a wind tunnel, then blasted it with smoke. Using a strobe light to freeze motion, they snapped 3- D pictures of the moth flapping wildly in the gale.

But insects are also nature's helicopters, with their wings acting as helicopter blades. To fly forward, bugs tilt their bodies forward, pulling air from in front and pushing it out behind as they flap wings back and forth. To hover, they tilt their bodies upward and fan wings horizontal to the ground, blowing air straight down so they can hang in midair. But, says Dickinson, there's still a lot of mystery surrounding insect flight. "We don't know what the animal does to initiate and control such forces, and it's going to take a lot more work by scientists with different specialties to find out."