Owls do hibernate during the winter season. The exception is the snowy owl, which migrates to warmer areas when winter comes around.
Similar to bears and other mammals that hibernate, owls store up body fat to make it through the winter without eating. During the fall months, the owls begin consuming more food and finding a suitable den that is safe from predators. When winter hits, the birds go into true hibernation. During hibernation, their core temperature drops, and their heartbeat slows dramatically. During this deep sleep, they do not eat, and their bodies use fat to stay alive. Some owls will waken from hibernation if danger is present. This happens when a predator penetrates the den or comes too close to the owl.