Ruby-crowned
Kinglet,
Regulus calendula
Ruby-crowned Kinglets are common wintering birds in the SF Bay Area; they sometimes allow close approach, but they are very small and constantly moving, and are hard to capture out in the open. They are similar in appearance to Hutton's Vireo, but have smaller bills and dark feathering below the larger wingbar.
The bird above shows the red crown feathers for which the species is named; these are often invisible.
