You will remember when a bird crashed through the window and...

You will remember when a bird crashed through the window and fell to the floor. You will remember, those of you who were there, how it jerked its wings before dying, and left a spot of blood on the floor after it was removed. But who among you was first to notice the negative bird it left in the window? Who first saw the shadow that the bird left behind, the shadow that drew blood from any finger that dared to trace it, the shadow that was better proof of the bird's existence than the bird ever was?