Owls hunt at night (they are nocturnal), which helps them a couple of ways. Much of their prey are also nocturnal and because their prey are active at night they are more likely to catch something. Because their feather design allows them to fly silently, and they are already camoflaged very well, hunting at night makes it even less likely that their prey will see them in time to escape.
Grizzly bears survive the winter by hibernating, which is a state of dormancy. They spend much of their time preparing for hibernation - they consume large quantities of food so they may store body fat to keep them warm and provide their bodies with enough energy to last through hibernation. Bears will also eat things like twigs just prior to hibernating so that they will not defecate while hibernating. During hibernation, the bears will live off of their stored fat, their metabolism will become extremely slow. Because of this, Hibernating allows them to survive the winter when there is not much food available. Mating is timed so that females will give birth in the spring, just after hibernation, so that food will be available for the females to nurse.