And then my camera landed on this bird:
A Hermit Warbler (Setophaga occidentalis)! Although more common during the summer and as a spring/fall migrant, Hermit Warblers are rare in Sonoma County during the winter. Most of them spend the non-breeding season between Mexico and Nicaragua.
Not sure how long this flock will stay together, but if you're near the Bodega Dunes Campground and run into some Townsend's Warblers, you might want to keep an eye out for a Hermit, too.