Hummingbirds nearly shut their bodies down every single night

To survive till dawn without starving, many hummingbird species enter nightly torpor: body temperature can fall from around 40C to as low as 10-20C, metabolic rate drops by 60-95%, and heart rate can plunge from over 1,000 beats per minute to under 50. It is a nightly near-hibernation forced by how fast their tiny bodies burn fuel.

— Wikipedia contributors, Torpor — Wikipedia, 'Torpor' article, hummingbird section