Bird Respiratory System

The avian lungs are pretty neat, and can be considered an improvement over the typical mammalian lungs.

Avian lungs have air sacs that extend into bones and muscles. The air sacs act as bellows to directly deliver oxygen to sustain the high metabolic rate needed to enable flight.

Below is a picture with better description of the unique avian anatomy:

(Taken at the Jurong Bird Park, Singapore)