A couple years back, when I was hiking in Shenandoah, I was trying to figure out what kind of bird was making this loud squeak noise as I moved down the trail. The bird always seemed to be hidden and on the ground. But it made one heck of a loud squeak. Then I realized that it was not a bird that I was hearing, but chipmunks. I heard that sound in my backyard today. Here is the culprit. He was stuffing his cheeks full of the birdseed that fell to the ground under my bird feeder.
Either his tail has been through some trouble, or I did not realize how funky chipmunk tails really are in the first place.