Hay Bob,
In my experienceat shootin birds, I have found that you only have half of the target that you are shooting at. Most of what you see is feathers, and if you place your shot in the front half center of the bird, you will most often take them clean.
In all my hunting, I have found that hunters shooting for a spot or point on the animal, are far more successful than hunters that shoot at the animal. When you ask them where they were aiming, they reply at the heart and lungs, but of those found are hit center in the stomach area.
I have seen experienced hunters fire into the ground, and swore they had the deer in there sights, another adrenaline driven problem of some hunters.