Tom, this is beautiful! How in the world you got this image with a 2/8 aperture is beyond me. It looks sharp from beak to tail!
Normally, having the bird flying away from you would be a problem but he turned that head back and gave you the once over and wow, does that add impact! The angle of the bird to your camera is also very strong - we get to see almost every area of the bird's body. The soft blues of the BG and the snow coming down really compliment the bird. It's a stunning image.
I like the soft tones of the image and agree that it's nice and sharp for f2.8. DoF increases with distance so if the subject was a long way off and this was a significant crop, it makes more sense. Although the slight head turn saves the image, one imagines what could have been had the bird been flying toward you rather than away.