The gull was observed from the Moonstone Beach parking lot and was flying south. It soared briefly over the river mouth before disappearing around the bluffs to the south.
Distinguishing features include its bulkier build compared to Bonaparte's Gull, wing tip pattern, and its red bill.
Different chin patterning compared to these other two that I saw today.
https://www.inaturalist.org/observations/215335198
https://www.inaturalist.org/observations/215332429
So there were at least three of them out there this morning.
Kingbird or a different kind of flycatcher?