AIR SACS - Part of the Respiratory Systemby Sally BlanchardAir sacs are balloon-like parts of the respiratory system. They are internal fragile tissue-thin, bubble-like sacs that go from the parrot's trachea to different areas of the bird's body; the abdomen. the clavicle (collarbone) area, and even the humerus bones of the wings. They are used for air exchange (breathing), ventilation, body heat control and in control of flight.
I have met a couple of older parrots with a ruptured air sac in the clavicle area. One was a Festive Amazon and the other was a Blue and Gold Macaw. From time to time the air sac can puff up like a balloon and becomes pretty obvious. Sometimes the air sac will deflate by itself, slow gentle pressure can deflate it, but in some situations, it will need to be gently punctured by a veterinarian to let the air out - don't try to do this yourself!