|Variety of large Larus gulls on the beach seawall|
The adults are pretty easy; the immatures produce a certain amount of "check the feet!" as a response; when the obviously smaller gulls have the pink legs and feet of herring gulls, well. That reduces the options for what the larger and generally pretty dark immature gull could be.
Apologies for the terrible focus; manual focus with no tripod is not my best skill. (I thought the lens was having cold issues; it looks more like the camera body is having ring-focusing-motor drive issues.)