For those that are not aware, here is how auto ISO works, at least on the D5100. In the menu you set what the maximum ISO you would want the camera to climb to if it needs. You then set the minimum shutter speed you don't want to drop below. On the camera you can set any base ISO you want, but you might as well set to 100 ISO to start with. You then set your aperture in aperture priority that you want to shoot at. As the camera meters the scene and sets the shutter speed if it gets down to the minimum speed you set in the menu it will start to ratchet up the ISO to be able to get the exposure it has calculated. So the camera is still going to try to give you the lowest ISO it can use. So we are still going with lowest ISO possible, but we are also getting an automatic adjustment that will help get those shots we would otherwise miss if we had to set the ISO ourselves.
This shot was not one that was so rushed. And if I had been paying more attention I could have set the ISO lower as the sun came up. But I was enjoying the morning and nature so much I was sort of forgetting the mechanics of photography. The thing is that I should be able to get lost in the moment. The computer in the camera is very very good. So I should be able to get wrapped up in nature and the moment and the enjoyment of it all and not worry about the camera settings and the mechanical and technical parts of photography.