When I checked with binoculars, I was a little surprised to see this species:
This is a Douglas' Squirrel (Tamiasciurus douglasii). It's the first time we've seen one in our yard. Inland they follow the Sierra Nevada Mountains farther south, but along the coast this is close to the southern end of their geographic range. (One reference showed them in Sonoma and Marin counties; another extended the range to San Francisco.)
Douglas' Squirrels are small (~12 inches long) with gray on the back and orange below (see next photo). Note also the pale crescents around the eyes and the tufted ears.
The tail is relatively flat, and there is a nice dark stripe between the gray back and orange belly.
The claws are long, which helps in climbing trees.
Although this individual was feasting on sunflower seeds, Douglas' Squirrels are known for eating tree seeds (especially of conifers such as fir, spruce, and hemlock) and fungi (e.g., truffles and other mushrooms).
This one also stopped for a drink of water at our bird bath.
It will be interesting to see if it comes by again.
I don't spend enough time in the woods, so if you have local sightings of Douglas' Squirrels or additional information about them that you'd like to share, please do!