To breathe, birds have lungs and humans have lungs, but birds breathe more efficiently than humans. Why is that?
Bird lungs take up more space in a bird’s body than human lungs in a human body. For example, a human’s lungs compose about 5% of its body, but a bird’s lungs compose about 20% of its body.
Birds breathe differently from the way humans breathe, and the way mammals breathe.
Birds have lungs and they also have air sacs. Depending on the bird species, some have 7 or 9 air sacs. Humans don’t have air sacs.
Bird lungs are in their chest (so are human lungs), but their air sacs are located in the humerus bone (the bone between the shoulder and elbow), the femur (thigh bone), the vertebrae (back bones), and even in their skull (head bone).
So, birds breathe air into their chest and into their bones. Having air sacs in their bones makes their bones extremely light, which they need to be able to help them fly (and of course they have other features, such as wings, for flying).
Birds have air sacs to keep oxygenated air in their body moving around, in one direction, throughout their respiratory (breathing) system.
Birds do not have a diaphragm, whereas humans have a diaphragm to help the lungs breathe. In birds, pressure changes in the air sacs helps them breathe. The chest muscles of birds cause their sternum to push outwards, making air go into their respiratory system. Other muscles then increase the pressure on the air sacs to push air out. So, the air goes in an out of their respiratory system (lungs and air sacs).
Bird lungs are more efficient than human lungs, and mammal lungs, because each breath has oxygen that goes to many different parts of the body – chest, shoulders, elbows, thighs, back, and head – all almost at the same time. This means that there is a lot of rich oxygenated air in the body of birds.
Birds need to have an efficient respiratory system because they have high metabolisms to enable them to fly. Humans don’t fly so they don’t need the same respiratory system as birds.
Photographer: Martina Nicolls
Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM