You know, I like to think I have a pretty good grasp on science, and biology, and how the world works. And then some little fact trots along and knocks me right on my butt, thereby pointing out that the world is far more strange and complicated than we sometimes give it credit for.
This is one such fact, which I stumbled over last week: birds breathe in only one direction. Most animals, such as ourselves, have "bidirectional respiration." We inhale, fresh air comes into our lungs, it gets exchanged for all the carbon dioxide and other waste products, and then the old air is exhaled. Fresh air in; stale air out. This is also called "tidal respiration," because it's similar to the way the tides move in and out.