Mystery Duck stands on one leg beside a temporary pond created by heavy rains about two weeks ago. When I stopped to take this picture, I thought it was a male Mallard, but even a cursory examination of the photo shows that assumption to have been mistaken. I'm not really sure what species it is, but Northern Pintail seems a likely prospect. For some reason, the authors of field guides seldom give photos or drawings of the rear ends of birds, favoring frontal and profiles views.