I can't think of anything spookier than howling coyote skeletons.
When I was in middle school my friend and I begged our parents to let us spend the night in a tent in the woods. Everything went great until the sun went down and this unearthly noise started echoing all around us. Our minds raced wondering what horrible thing it could be. Ghosts? UFOs? Around midnight we decided to make a break for it and spent the night inside. It turned out to be nothing more than a couple coyotes having a conversation. Those howls at night still give me the chills.