Birds have a unique respiratory system.Brids need a tremendous
amount of oxygen to gain energy
for flight,so they have developed a different respiratory system.Unlike mammals,the lungs of birds do not inflate or deflate as they breathe on and out.Instead,they have air sacs which are like tiny air bags in cars.These air sacs ventilate air,leaving their lungs full of air items.The process of oxygen circulation through the body in birds is done through small blood vessels.