The conversation between human and AI assistant.
Why don't birds fall down while sleeping in trees?
Oh, I see. What about when they're sleeping while flying? How do they avoid crashing into things?
Most birds don't sleep while flying, except for birds like swifts and frigate birds. When these birds sleep while flying, they use a technique called unihemispheric slow-wave sleep, which allows one half of their brain to sleep while the other half stays awake to control their flight path. This allows them to avoid crashing into obstacles.