National Geographic: Birds are the planet's superheroes, built for survival.
The ice of Antarctica doesn't faze them. Nor does the heat of the tropics. They thrive in the desert, in swamps, on the open ocean, on sheer rock faces, on treeless tundra, atop airless mountaintops, and burrowed into barren soil.
Some fly nonstop for days on end. With just the feathers on their backs, they crisscross the hemisphere, dodging hurricanes and predators along the way, arriving unerringly at a precise spot, year after year....