Which animal would be able to unscrew a light bulb?
It’s possible that a raccoon could do this; it’s the only animal that has the dexterity to remove a bulb. Lacking fully opposable thumbs, it would have to use both “hands,” probably perching on the railing or bracing its back feet on the post.
Raccoons would do this in early March, when they have just come out of hibernation and are hungry. A light bulb may have a human scent on it, and as raccoons have learned, where there are humans, there’s food. Once a bulb is on the ground, any number of critters besides the coon could be interested enough to take a nip at it.