In the interest of keeping the fire going, I went to get some small sticks from the shed that the hens share with the woodpile. When I stepped in, I saw the hens were roosting, their feathers all puffed out against the cold. I checked to see that their water wasn't frozen, then that they had food, then looked in the nest box -- where a skunk was helping him/herself to the eggs! With a muttered "oh, boy," I backed out, shut the door, and came to announce the visitor to Jeff. Long story short, he shot the skunk and threw it over the fence into the pasture.
What we can't figure is why the skunk hadn't bothered the hens. Maybe this was a philosophical skunk who thought, "Eat a hen tonight, I eat once. Let a hen live, I have an egg dinner every night."