Seagulls seem to have some kind of pecking order since this one had no problem knocking off his pal and the pal didn't give up much of a fight. This happened repeatedly while I watched.
There are a large number of gulls in Peterson. Seriously, I had no idea there were so many types of gulls. In my mind, they are all just Jonathan Livingston (loved that book when I was a teen). I'm thinking this is a California gull because of the dark spot on its bill.