Agree with most of what Dan said, esp about the white, but I'd also like to see the bird a farther along in its flight (i.e. closer to crossing your shooting position) to minimize shadows and maximize
DOF across the subject. This bird has such awesome legs, and it's great when shot can have them fully lit and in focus. The bottom part of the BF is great, but the gray at the top is a bit distracting.
Excellent points made by Dan and Dorian. These birds are a lot of fun to photograph and you've captured the pose well. I wish the wings were either completely raised or fully downward as I find this pose slightly awkward. The light and background are really nice, although I do find the top half of the BG slightly distracting as well. Great effort though, especially considering the focal length you were at. TFS and looking forward to more!