How do bird stay in the air without flapping there wings?

Gliding: Defined as falling at less than 45 degrees from the horizontal. Lift caused by some kind of aerofoil mechanism, allowing slowly falling directed horizontal movement. Streamlined to decrease drag forces to aid aerofoil. Often some maneuverability in air. Gliding animals have a lower aspect ratio (wing length/wing breadth) than flyers. 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. The lift force occurs because the air has a lower pressure just above the wing and higher pressure below. When gliding, both birds and gliders obtain both a vertical and a forward force from their wings. This is possible because the lift force is generated at right angles to the air flow, which in level flight comes from slightly below the wing. The lift force therefore has a forward component. High aspect ratio wings, which usually have low wing loading and are far longer than they are wide, are used for slower flight, almost hovering (as used by kestrels, terns and nightjars) or alternatively by birds that specialize in soaring and gliding flight, particularly that used by seabirds, dynamic soaring, which use different wind speeds at different heights (wind shear) above the waves in the ocean to provide lift.