Wikipedia:Picture of the day/December 11, 2006
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A male Mallard in mid-flight. The fundamentals of bird flight are similar to those of aircraft. Lift force is produced by the action of air-flow on the wing, which is an airfoil. This occurs because the air has a lower air pressure just above the wing and higher pressure below. When a bird flaps its wings they continue to develop lift but they also create an additional forward and upward force, thrust, to counteract its weight and drag. Photo credit: Alan D. Wilson |