Although I saw a Chestnut-sided Warbler (Setophaga pensylvanica) on 27 September 2012, I wasn't able to get any pictures that day. Today we found the warbler in the cypress trees near the Bodega Marine Lab housing area, and then later in Owl Canyon.
This is a fall bird, most likely a female, so there isn't any chestnut on the sides where it would be in breeding plumage. Instead you'll notice the bright green crown and back, and white underparts. The green color really stands out!
Here are a couple of views showing the white eye ring.
And one more where you can also see the bold wing bars.
A Blackburnian Warbler continued to be seen in the cypress trees near the BML housing area today. For the record, here are a few more photos of this rare vagrant.
Both of these warblers have more easterly breeding distributions, generally found in northeastern North America. Chestnut-sided Warblers winter primarily in Central America and Blackburnian Warblers winter in Central America and northern South America. They're rare on the West Coast, e.g., in Sonoma County over the past 45 years , there are ~55 records for Chestnut-sided Warbler and ~15 records for Blackburnian Warbler.