Q: This weekend while cleaning up my backyard I encountered an unexpected resident in our bluebird house. I cannot see the tail or markings. I look forward to your reply.
A: You have a flying squirrel! They commonly make their homes in tree hollows (and sometimes in attics) so it isn’t surprising that they’d find a bluebird house inviting.
Since the squirrels’ activities are strictly nocturnal, most folks aren’t aware of how many actually live in their landscape trees.
If you hear high-pitched squeaks up in the trees on a still summer night, you’re hearing flying squirrels. Shine a flashlight up between tall trees and you can sometimes see their white underbellies as they glide from tree to tree.
They can be a real nuisance if they make a home in your attic: lots of “thumps and bumps” in the middle of the night. I recommend using a live trap to catch and relocate them if they become troublesome.