You're getting a lot better pictures of the hummers than I am. I think that it may be a combination of you having a better camera, lens and the fact that they are probably slower because of the heat there in Louisiana.
I'm still using an old D 300s and a Nikkor 70-300mm ED zoom lens. My Nik 300mm f/4 lens is a little too long as I sit only about 15 feet away.
I can't wait to see how the new D 500 pans out in reviews and if problems show up.