I like the wing position. It makes the duck look like a soaring hawk. I like how he is tilted towards the URH corner of the frame with plenty of flying space. The under wing and belly details are great, but the shadows are somewhat harsh.
The head angle looks good to me, but I'm relativity new to this. The background is a bit distracting (sailboats?).
All and all I would be happy if I had a flight photo like this.
Great focus with the 2X converter....I like the HA just fine. I would attempt to tone down the bright areas in the BG....they are somewhat distracting but wow you nailed the bird just right IMHO:)