Backyard Creature

I studied zoology in college. Lots of anatomy, behavior, and physiology of animals. Sometimes I like to take my learnings and observe the wildlife in my backyard. For example, watching a male bird do an interesting jig on the power line to attract a mate
or see a squirrel claim a tree and its nuts as his by chasing away all other squirrels. But what I saw on Saturday was beyond explanation and not in any textbook I've read. Only wish little Joe had been here to see this. Notice the black creature going
crazy in response.