Gas exchange, oxygen transport and metabolism in high-altitude waterfowl.

Summary: Imagine trying to run a marathon while breathing through a thin straw. That is what it feels like to be high up in the mountains where the air is very thin. Yet, some birds, like the Bar-headed Goose, fly over the highest mountains in the world without any trouble. How do they do it?

This paper explains that these birds are like natural super-athletes. They have larger lungs to take in more air and special blood that grabs oxygen better than other animals. Their hearts are stronger, and their muscles have more tiny blood vessels to keep them fueled. While humans might faint at those heights, these birds have evolved amazing body hacks to keep flying high.