Oak Titmouse. Hot Springs Mountain, California. April 13, 2014. Greg Gillson.
There aren't any Black-capped Chickadees this far south. There are, however, Mountain Chickadees in the hills and sometimes, inexplicably to me, in residential areas of San Diego throughout the year. Instead, the Oak Titmouse is the local chickadee representative found in oak canyons, but not residential backyard bird feeders away from oaks--they are very reliant on their preferred habitat.
The larger oaks are inland. The smaller live oaks nearer the coast are not as desirable. Thus, these birds are more common farther inland in the county.