Bird lungs are connected to a system of air sacs. These air sacs help improve lung efficiency and also help the lungs provide a cooling system that removes the large amounts of excess heat produced by flight. Birds have four - chambered hearts which enable the well oxygenated blood to pass quickly to the flight muscles. A final important adaptation allows successful flight. Bird feathers are both light and strong.
Feathers provide a light, warm coat.
Even more important, the feathers create a streamlined shape that allows for efficient movement through the air.