How Do Birds Breathe?

Steve Jurvetson/Flickr/CC-BY-2.0

While birds inhale oxygen and expel carbon dioxide through their mouth or nostrils just as mammals do, their respiratory systems are more complex than those of other animals. Birds feature organs called air sacs that connect to their lungs. These air sacs extend into some of the hollow bones of birds and increase the amount of gas inside their bodies at all times.