Among air-breathing animals, why do birds have the most effective mechanism of extracting oxygen from air?

Question

Quizplus · Accepted Answer

Birds utilize crosscurrent exchange, where oxygenated air flows in one direction and blood flows in the opposite direction, allowing for a greater exchange of gases in the lungs. This mechanism is more effective than the tidal exchange mechanism used by other air-breathing animals. Additionally, while birds do have air sacs that provide additional respiratory surfaces, the size and surface area of their lungs are not significantly larger than those of other air-breathing animals.

Among Air-Breathing Animals, Why Do Birds Have the Most Effective