Immature Laughing Gull.
Note that the grey plumage is taking over the territory on his back and topside of wings, formerly occupied by brown, and the beginning of a black "hood" on his head.
When fully mature, his head and face will be solid black, and his wings (topside) will be silvery grey with black tips, while the underside of his wings will be white with black tips, as in THIS EXAMPLE.
Lake Emerald, in Oakland Park, Florida -US- near Fort Lauderdale.
Shot from my balcony over the lake, Monday afternoon, April 24, 2006.
See him LARGER.