Nice gull, Craig. I like the BG but one thing to try to watch is getting a wave right across the back of his head. If you can avoid that next time (also happens with the horizon line so be careful there, too!) it will strengthen your composition.
It seems like the dark bird feathers and darker areas of the BG have quite a bit of noise going on. The water looks a little oversharpened so go back, remove the sharpening and check the noise in those dark gray feathers and see if they came from sharpening or if they are due to a low exposure. If if happened while sharpening, resharpen slowly in steps and see when the noise gets introduced.
Nice movement and HA on the bird and you did a very nice job with your choice of crop and the position of the bird in the frame.
beautiful bird - lovely detail in the white feathers against the grey feathers of the side --- good advice from Julie and Dave, would love to see a repost....