here are a few shots with the new Sigma 100-400 Zoom. Picture one is a turtle in a pond this sucker is about 12 inches long. The second picture is a Malliard duck posing for me about 40 ft away And the third is Downtown L.A. in a lot of Haze. I used the DeHaze filter from LR to DeHaze it.
You may be better served by a D500 and the Nikon 200-500 zoom.