Well just to be awkward ... Im going to disagree with the above!
I actually think the crop works well because although the Gulls are the main focus, I like the way the outline of the back of the nearest bird reflects the symmetry of the steps/rail and leads my eye to the boats behind, then my eye comes back to the heads of the birds.
For me the only thing really marring the shot is the blown highlights on the back of the birds necks.
Still a nice colourful shot though, which you dont see very often where Gulls are concerned!