Stand on the north pier at low tide and you will see four kinds of gull working the breakwater, usually within a few feet of each other and usually arguing. Telling them apart takes about a week of practice and this guide.
The regulars
The largest and loudest is the western gull, gray-backed with a heavy yellow bill and a red spot near the tip. It is the bird that will take a sandwich from an open hand if you let it get close enough, and the one most likely to win a fight over a dropped fry.
Smaller and paler is the ring-billed gull, easy to spot by the thin black ring near the tip of its bill. They travel in loose flocks and tend to keep their distance from the western gulls, which outweigh them by nearly a pound.
The California gull shows up mostly in fall and winter, dark-eyed with a red and black spot on the bill instead of a single red mark. It is the most likely of the four to be seen far from the water, working the parking lot behind the fish market.
The one that is not a gull
The bird most often misidentified as a gull on the pier is actually a Caspian tern, sharp-winged with a heavy orange-red bill and a black cap. Terns dive for fish rather than scavenging, which is the fastest way to rule out a gull if you catch one in the act. Watch the water for a moment and the difference becomes obvious: a tern hovers and drops, a gull mostly just waits for something to be dropped for it.
The fries question has an easy answer. Western gulls win most contested food because they are the biggest bird on the pier and the least likely to back down. Size settles most arguments here, the same as it does at the council microphone on a Tuesday night.
Fall brings a fifth, less common visitor worth watching for: the Heermann's gull, dark gray with a bright red bill, usually arriving in small numbers after breeding season further south. It tends to keep to itself near the far end of the breakwater rather than joining the scrum at the fish market end.
Bring binoculars if you have them, and give the birds room. A gull that has learned to take food from hands is a gull that will eventually get hurt trying.
