So there are several varieties of gulls, and some hang out near the ocean, but gulls are differentiated by size and not by color, as some species change the color of their plumage as they mature. How human of us to assume that brown gulls, gray gulls and white gulls are different species.
Gulls are common around the Great Salt Lake in Utah, and do not seem to fly in from the coast, as was once thought.
Whatever gulls are, there are relatively few of them in the DR. I do not think that it would be am improvement if there were more, but a lot of whatever a gull eats in Miami is also available in any dump in the DR, so there absence is somewhat surprising.
Pigeons, it seems that everyone has pigeons. I have never been to any pigeon-free place. I am thinking that there probably are few in Nunavit, Greenland, Patagonia or perhaps Mongolia, but I have not been there.