|Man has always envied the ability of birds to soar
through the air with complete freedom. Flying is now commonplace, but even
an expert hang glider cannot match the natural skill of a bird. The bird
is a well designed flying machine with strong muscles, lightweight bones,
and complex wings. Wing shapes differ according to lifestyle – forest dwellers
have short, stubby wings for swerving through trees and undergrowth while
seabirds have long, slender wings so they can cover vast distances with a
minimum of effort.
Flight: Birds fly in a variety of ways. Active or flapping flight is used for taking off, turning, landing, and moving quickly from place to place. The wings flap in an energetic and exhausting rowing action, sometimes in a figure eight rather than just up and down. To save energy, many birds glide on outstretched wings in between short bursts of active flight. The direction of the wind affects their ability to stay aloft. Large birds glide often, while small species glide very little.
In hot countries, birds fly long distances by soaring, which is a form of gliding. Rising thermals (currents of warm air) carry them into the air, keeping them up without the birds’ flapping their wings. Birds also hover. The hummingbird stays in place when feeding by rapidly flapping while its body and head stay still. It can hover backward and forward by rapidly rotating its wings in a figure eight motion, lifting and keeping its body stable. A hummingbird beats its wings 50 to 70 times each second to keep its bill steady as it feeds.
Taking Off and Landing: Birds use tremendous energy to take off. They accelerate rapidly so they will not stall and fall to the ground. Small birds leap into the air and fly, but larger species’ weight poses a problem. Weighing up to 26 pounds, the wandering albatross takes off in strong head winds to get sufficient lift. Some larger birds run on the ground to gather speed, while others “fall” into the air from cliffs. Water birds such as the mute swan use a “runway” across a stretch of water. To land, these birds raise and spread the alula (feathers on the front wing edge), which act as brakes. Some species use their tail feathers as stabilizers and brakes.
Wings and Feathers: A birds flapping wings keep it airborne and moving forward through the air. Wings can twist, fold, flap, and spread. In flight, the large pectorals major muscle pulls the wings downward and the smaller pectorals minor muscle pulls them back up, helped by the birds weight against the air. For flight, the primary and secondary flight feathers give the wings a smooth, aerodynamic covering any way they fold or turn. The feathers also separate to allow air to pass through them when landing. Tail feathers direct maneuvering or braking in flight.
Wing and body size must be balanced for flying. New Zealand's kakapo, or owl parrot, has well developed wings, but its body is too heavy for flight. It can only glide downward for short distances. The kakapo’s body weighs up to five pounds, but its flight muscles are only three to four percent of the total weight. They do not have enough power to raise the body off the ground into active flight.
Speed and Distance:
Fast Flyers: The peregrine falcon flies at 60 miles per hour in normal flight with spread wings, but it sweeps its wings back and reaches dive speeds up to 150 miles per hour to catch prey. The sleek swift flies up to 62 miles per hour during aerobatic displays over rooftops, but it flies slowly when trying to catch insects in flight. Ducks have some of the fastest speeds for steady, direct flight. The eider duck, with its strong wings and flight muscles, can fly at tremendous speeds downwind. The puffin propels itself through water using strong, stubby wings to force it deeper when tracking fish. On land, it makes clumsy landings.
Long Distance Travelers: Also known for its fearless dives on intruders at nest sites, the arctic tern is one of the most widely traveled birds. It often migrates 22,000 miles round trip to its breeding grounds. One arctic tern traveled 11,185 miles in less than three months. The arctic terns elegant form is instantly recognizable. Nesting on icy coasts of the far north, it journeys half way around the globe to reach warmer wintering grounds.
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