The biology of pegasi (headcanon) · 8:02pm Feb 14th, 2017
Headcanon: wings are, at least partially, connected to the autonomic nervous system. Why? The autonomic nervous system controls functions of the body that are unconscious, for example heart rate or digestion. Meanwhile, pegasi can apparently use their wings while asleep:
Every year, about twenty pegasi are killed or injured when they fall asleep mid-flight and crash into windmills.
Note that some birds do sleep while flying, though the mechanism is a bit different. But remember that autonomic nervous system also controls sexual arousal, which would explain wingboners.
That pony sure does love books
Headcanon accepted!