How do birds breathe?
Birds are characterized by the so-called "double breathing". In addition to the lungs, birds also have air sacs, which exceed the lungs by several times in volume. Gas exchange occurs only in the lungs, but thanks to the air sacs, oxygen enters the blood both during inhalation and exhalation.
Birds breathe lungs by stretching and compressing air sacs. The lungs are composed of feathers from very thin tubules. The lungs are small ones. Thanks to air sacs, respiration causes the exchange surfaces of the pulmonary tubes to take a lot of oxygen from the air.