Owls can turn their heads 270 degrees without cutting off blood to the brain

Owls can't move their eyes in their sockets, so they compensate with necks that rotate roughly three-quarters of a full circle. Imaging studies found owls have extra blood reservoirs at the base of the skull and vertebral arteries that expand, keeping the brain fed even as the twist would pinch off blood flow in almost any other animal.

— Fabian de Kok-Mercado, Michael Habib, Philippe Gailloud, Blood supply to the brain and eyes in the rotated head position of owls — Johns Hopkins University research, presented 2013