From my bobbing boat yesterday on Lake Toho, Kissimmee, Fl.. I wish I had been able to capture him from a tripod but I was packed up and heading back to my slip when I noticed him.
MKIII, EF500@1.4x, 1/125, f/5.6, ISO 640, E.C. +1, hand held. Eliminated a couple little twigs left of his neck.
The point of focus must have been on the body or bill, as that is sharper than the eye. I might do another pass of USM, esp. on the eye to bring it up.
The head position is just so that I miss the other eye. If it was turned more to the right, I don't think it would bother me.
The framing and light look great. On the Mark III, I would push the ISO a bit higher in low light to get faster shutter speeds. Might have given you a little more sharpness.
I like the base composition. nut too loose of the left side for my taste. Did you clone BG out of the left side of the bird? The outline is kinda funky.
The red channel must be blown out of reach, meaning you could cool the temperature a bit to avoid the "hot" look.