Happy to say my critter in the willow tree has left for a more comfortable perch. We don't have bears in the part of Maine I live, at least I don't think we do. We also don't have possum in my neck of the woods, too cold I think.
From now on when I'm doing yard work I'm make sure to look up before I begin. I wasn't afraid to hit the tree with a downed small branch because I made sure to step out of the way when I did. Two of my dogs years ago got a mouthful of quills in their mouth and snout that had to be removed by a vet who had to tranquilize them first. I sure don't want to go that route again.
All's well that ends well I say and how that not so little guy or gal managed to stay on that tiny little branch is beyond me :-)