I like that it's a duck, but I don't like that I need a few moments to figure that out. A nice idea, marred by a dark, muddy, unattractive execution. Sorry.
Good stop motion and tracking of subject.
Placement of subject moving out of image throws the whole balance of the picture off and the dark vs light horizon, makes the image appear tilted in just the wrong direction as well. The duck's coloration blends too much with the river's shadows.
Great Tracking - Poor Image.
Nice job of panning. Two things that might help improve the image: (1) have more space to fly into rather than behind the bird (that helps with the sense of movement); (2) try to get a dark bird like this against a different colour background, lighter or so, to set it off - as it is, the bird, especially the wing areas, gets lost agains the background.