We don more layers of clothing as the temperature plummets.
Some birds migrate as the day length shortens and before it gets very cold.
Pygmy Nuthatches snuggle tightly to keep warm during a sub-zero storm. The Chickadee and Tufted Titmouse fluff their outer contour feathers, trapping insulating layers of air between the soft down feathers near their body. Bobwhites roost in a circle to fight off the winter chill. Moths and butterflies pupate into a state of dormancy wrapped in their silk cocoon. Fish, if the oxygen is cut off because the lake is too shallow will die.