Now is a perfect time to notice the nests, or dreys, of gray squirrels. Gray squirrels build these dreys in branches of trees and they are obvious when not hidden by leaves. Squirrel dreys have always seemed a bit flimsy to me from my vantage point on the ground and I can't help but wonder how warm they are, as gray squirrels remain mostly active in these cold days and nights of winter. I recently was re-reading a section of Bernd Heinrich's Winter World, the ingenuity of animal survival and found a paragraph where he describes a drey that has blown down in a rainstorm. Heinrich describes a well-constructed and cozy home inside the haphazard array of twigs and leaves that we see from the ground. Just inside the outer shell were layers and layers of oak leaf "shingles", making it water tight. And within that were 4cm of "finely shredded" inner tree bark.
Thank you to Bob Gore for the photograph.