This image is very distant (from the State Park at Paris Landing), but shows how obvious an adult type Lesser Black-back is among the Herring and Ring-billed Gulls. Not too often you get 2 adult Lesser Back-backs near side-by-side, and there was also a 2nd-winter bird which I couldn't get into the same frame. Notice the intermediate size of the Black-backs with the Herrings and Ring-bills in the photo.