They flap only for liftoff or to gain altitude. When they're high enough, they glide.
ANSWER
It depends on the bird. Some birds, such as most raptors, soar on the air currents like gliders while they search the ground for prey. Some, like Hummingbirds, would drop like stones if they stopped flapping. Some will flap for awhile, then rest as the propulsion carries them forward, and then flap some more.
You really have to check each species of bird in order to find out how that particular species flies.
swallows
Because of their wings and the wind speed outside.
The purpose of the air sacs in a bird is to help digest food into the gizzard, and to help it breathe, and stay in the air longer and more smoothly. Hope this helps!
Birds are able to stay airborne while seemingly flying in place due to a phenomenon called "dynamic soaring." This involves the bird using the wind patterns and air currents to generate lift and maintain its position in the air without expending much energy. By skillfully maneuvering in these air currents, birds can effectively stay in one spot while in flight.
Air+Lizard= Bird
A humming bird
15 psi
An Experiment on a Bird in the Air Pump was created in 1768.
The buoyant force of air would be greatest for a hot air balloon because it relies on the principle of buoyancy to stay aloft. The heated air inside the balloon is less dense than the surrounding air, creating a greater buoyant force to lift the balloon. A bird and an airplane rely on aerodynamic lift generated by their wings to stay airborne, rather than buoyancy.
No, they stay where they live.
the air-y bird
air+egg=bird