Home  Birds About Birds Biology Flight
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The ability to fly is a major feature of most species of birds, though some birds such as emus and penguins are incapable of flight. Although some other animals, such as bats, are able to fly, birds have many highly evolved characteristics which allow them to fly more efficiently. The first of these is that birds are generally light-weight, and birds have many features of their skeletons which minimize their weight. Birds’ bones are usually not solid, but are hollow or contain air sacs, which allow air to circulate to make the bird lighter. These bones are supported by internal struts which brace the bone to give it extra strength. Other weight-reducing features of a bird’s skeleton are that it has few joints within its skeleton; they lack teeth; and feathers are also light weight. Birds also have exceptionally well-developed breast muscles which allow them to flap their wings.
How do birds fly?It seems obvious, but birds fly by flapping their wings. It takes lots of strength to flap a pair of wings, so birds have developed large muscles for the task, and the size and shape of the sternum (breastbone) of a bird is enlarged to attach the muscles to the skeleton. It is, however, the shape of their wings which provides the lift birds need to become airborne. The upper surface of each wing is convex in shape and slightly longer than the underwing, which is concave. As the bird flaps its wings, air is forced both over and beneath each wing, and the difference in air pressure caused by the shape of each surface forces the bird upwards. All birds that can fly have convex and concave surfaces on their wings, but the overall shape of the wings varies greatly, and determines the type of flight that the bird does. Birds with long, pointed wings, such as Peregrine Falcons or Fork-tailed Swifts, are capable of high-speed flight; those with shorter, more rounded wings, such as Superb Fairy-wrens or Brown Goshawks, generally do not fly very quickly but are able to manoeuvre deftly between obstacles such as trees or shrubs in the forest; and birds with long, narrow wings, such as Shy Albatrosses or Australasian Gannets, can glide for long periods without flapping their wings at all.
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Peregrine Falcon in flight © Glenn Ehmke
Mulga Parrot in flight at Hattah VIC © Chris Tzaros
Wedge-tailed Eagle in flight © Dean Ingwersen
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