Here are the two birds in one photo. You'll notice that one is paler than the other.
Closer views highlight the color differences, with one being mostly white below and the other showing quite a bit of yellow below (along with a rusty cap) — see next two images.
Palm Warblers are only accidental winter visitors to Bodega Bay. (They're casual fall vagrants in this area. They breed much farther north, in the bogs and fens of Canada and the northern U.S.)
Somewhat unusual among wood-warblers, Palm Warblers are ground-feeders. These two were actively searching the washed-up kelp for insects. Note the pale supercilium (eyebrow stripe) and the bright yellow undertail coverts.
Here are a few more fun images:
P.S. If you're wondering: "Palm" is a little misleading for this warbler. Although the first specimen was collected in the Caribbean, they're a more northerly species than the common name would suggest.