Oak Titmouse (Baeolophus inornatus) resident from southern Oregon south to Baja California. Preferred habitats include live oaks and deciduous growth.Reference
identify.whatbird.com/obj/138/_/Oak_Titmouse.aspxWhilst I was observing the two titmice trying to build the nest, they were severely harrassed by a female Nuttall's Woodpecker. I have been back to this potential nesting hole many times in the last 4 weeks but the titmice obviously chose to nest elsewhere.