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Bird flight is the primary mode of locomotion used by most bird species in which birds take off and fly. Flight assists birds with feeding, breeding , avoiding predators , and migrating . Bird flight includes multiple types of motion, including hovering, taking off, and landing, involving many complex movements.
Birds (flying, soaring) – Most of the approximately 10,000 living species can fly (flightless birds are the exception). Bird flight is one of the most studied forms of aerial locomotion in animals. See List of soaring birds for birds that can soar as well as fly. Townsends's big-eared bat, (Corynorhinus townsendii) displaying the "hand wing"
These were gradual changes, though, and not strict conditions for flight: the first birds had teeth, at best a small keel and relatively unfused bones. Pneumatic bone , that is hollow or filled with air sacs, has often been seen as an adaptation reducing weight, but it was already present in non-flying dinosaurs, and birds on average do not ...
Bird anatomy, or the physiological structure of birds' bodies, shows many unique adaptations, mostly aiding flight.Birds have a light skeletal system and light but powerful musculature which, along with circulatory and respiratory systems capable of very high metabolic rates and oxygen supply, permit the bird to fly.
Exaptations include the co-option of feathers, which initially evolved for heat regulation, for display, and later for use in bird flight. Another example is the lungs of many basal fish , which evolved into the lungs of terrestrial vertebrates but also underwent exaptation to become the gas bladder , a buoyancy control organ, in derived fish ...
Birds have various adaptations for flight, including a lightweight skeleton, two large flight muscles, the pectoralis (which accounts for 15% of the total mass of the bird) and the supracoracoideus, as well as a modified forelimb that serves as an aerofoil.
Because birds fly at an angle relative to the wind during dynamic soaring, they must be able to achieve flight speeds greater than this head wind. Consequently, birds that rely on dynamic soaring tend to have low wing loadings and high aspect ratios. In other words, gliding birds have wing shapes that allow them to behave more like fixed wing ...
The WAIR hypothesis for the origin of flight is a version of the "cursorial model" of the evolution of avian flight, in which birds' wings originated from forelimb modifications that provided downforce, enabling the proto-birds to run up extremely steep slopes such as the trunks of trees.