Some animals survive because of layers of fat, and/or thick fur, such as my avatar, the Bactrian camel. There is at least one type of frog which self freezes. They secrete a fluid at the first sign of frost. This starts the process. They freeze in a hard little lump. When weather warms, they thaw right out and immediately look for a mate. (Should have thought of that before the cold.) I’m not sure how sparrows manage, but I could swear the other day I heard one say, “Jeez it’s cold!” A duck nearby became offended and said, “At least you don’t have to keep yourself watertight so your arse doesn’t freeze over!”