BIF a long way off

I took this shot with my new 5D3 (yes, I was a good boy last year) and 400mm 5.6 lens while I was waiting for my usual deck birds to show up. I know it's not a good shot but the Canada geese were just over 4,500 feet away. I've tried this shot before (give or take 500 feet) with the 7D and sigma 150-500 and the birds were not recognizable. I'm happy.

That's very good for something almost a mile away!