Flight Adaptations

Because of the large demand of aerobic respiration for active motions, modification of the lung system was necessary. Air is inhaled through the windpipe (trachea) and passes to the air-sacs before flowing through the lungs. The thin-walled air-sacs act solely as reservoirs; some penetrate the hollow bones. These air-sacs help in the aerodynamics of the bird; along with the feathers, they help in streamlining the body, without adding wieght.

Left: The structure of the modern birds lungs.