I was a little more than surprised when I spotted this bird on the way through the BML (Bodega Marine Laboratory) parking lot at the end of the day on 23 September 2012. I looked at it and realized that I wasn't quite sure what species it was!
It flew off into the depths of a shrub, but thankfully started to call which made it easier to find again. The most common call note was a clear whistle, which I've seen written as wheurr or whee-er. It also occasionally gave a chuck note, somewhat similar to that of a Hermit Thrush.
Luckily, it perched on the edge of a shrub just long enough for a few more photographs.
Above, note the overall brown/gray coloration (with some dark feather centers), streaks above and below, pale yellow eye, and two narrow white wing bars.
In the next photo you can see the relatively short and uncurved bill, mostly black with a pale base.
With a head-on view, note the dark stripes along the sides of the throat.
Although not visible in these photographs, the tail when spread had white corners (reminiscent of an American Robin).
This is a Sage Thrasher (Oreoscoptes montanus), formerly called a Mountain Mockingbird. They're casual fall vagrants to the coast, this being only the third record for Sonoma County! The last record was from 14 years ago on Bodega Head on 21 September 1998. The first was observed near Petaluma on 27 September 1986.
Sage Thrashers are the smallest of the thrashers. Although the westernmost breeding areas are in eastern California (associated with sagebrush), they're known for wandering during migration.
P.S. Thanks to many local and non-local birders for helping to confirm this identification!