How can Ruby-throated hummingbirds fly over the open water of the Gulf of Mexico for their annual migration, traveling nonstop up to 500 miles to reach shores of the United States, a flight of 18 to 22 hours?

This is a similar story, that the energetics are highly focused and finely tuned to maximize stamina and avoid the problem of fatigue from buildup of waste products which are processed much more efficiently than is the case in many mammals, including human. They have a special physiology, and as with squirrels, there is much to be learned by science here that can be exploited for human betterment.