Question

Birds that fly at high altitudes need an especially efficient respiratory system why?

Answer 1

Highly efficient respiratory system is required by them because at high altitudes their is less amount of oxygen.

Answer 2

It is true that birds are super efficient breathers. In case of other animals, air takes oxygen inside the body and brings carbon dioxide outside the body where in case of birds, oxygen gets in when a bird inhales and exhales. Besides lungs, birds have small air sacs attached with a tube. When air enters the mouth the oxygenated air enters to air sacs whereas the carbon dioxide from body exhales out through lungs. When a bird exhales, the oxygen rich air in the rearmost sacs enters lungs while carbon dioxide is exhaled out from the body by the front most air sac.