To survive the night, some hummingbirds shut their bodies down almost entirely

A hummingbird's heart can beat over 1,200 times a minute in flight, a metabolism so fast it would starve overnight without help. Many species enter torpor after dark, dropping body temperature by up to 30°C and slowing their heart rate to a fraction of its daytime pace, then rewarming and restarting their full metabolism again by dawn.

— Wikipedia contributors, Torpor — observed across multiple hummingbird species