A nest built in a short stump. The stump might have broken off after the female built her nest, leaving it open on top and exposed to cowbird parasitism. An associate saw to the demise of this cowbird, though I've seen Prothonotaries in other locations feeding cowbird chicks. I know it is not centered but I had to hold the camera above my head to take this and could just could not get a centered shot for the life of me!