Looks like a duck . . .

The next bird flies overhead and the pathologist looks at it, then looks through the pages of a bird manual, and says, "Hmmmm...green wings, yellow bill, quacking sound...might be a duck." He raises his gun to shoot it, but the bird is long gone.
A third bird flies over. The surgeon raises his gun and shoots almost without looking, brings the bird down, and turns to the pathologist and says, "Go see if that was a duck."
Originally published November 14, 2002.