This is a shot of a hawk in my garden. shot with the 5D3, 100-400L+1.4x @400 so effective 560mm. Yes, I upgraded last night! Yay! I have not AFMAed it yet so this was shot with live view. The settings were f8, 1/800, ISO 1600. You will notice that he has had a drink of water in the garden as well.So I assume you superglued him to a branch? I've had quite a few hawks in our garden (lots of small Birds in our garden so its inevitable that the hawks hunt there), no matter how slowly and quietly I try to get in position, they are off. I guess my only chance would be if I was sitting there when one landed.
Its certainly a great shot.