What IS that thing?

We were sitting out on the deck yesterday, enjoying our lunch when I spied something long and slender flapping in the breeze. It was about 25 feet up in our "dead" tree. We confirmed our thoughts using the binoculars - it was a snakeskin!

"Oh, my gosh!" I thought; Danny thought, "Awlright! A target!!" He ran for his guy, I ran for my camera.
I actually took a short video of him shooting up there, but it didn't show much. I did keep a photo. You can just make it out on that larger left limb, a whitish line following the upper curve of the limb. Enlarge to see it better.

After it fell to the ground we eye-ball measured it to be about 3 feet long. Guess I won't be going into the woods much until winter.