ocr: AIR SACS - BOUT ONE-FIFTH of a bird's body Aista - taken up by its breathing system. The lungs are quite small - most of a bird's respiratory system is made up of air sacs. Some diving birds have specially adapted air sacs that not only aid breathing, but also cushion the organs as the bird hits the water. The air sacs also provide buoyancy, which helps the bird bob back up to the water's surface. CUSHIONED IMPACT The slue-footea booby plunges into the sea from beights ofup to 100 feet (30 m) to catch fish. Its air SACS provide padding for its internal organs.
