Editor’s Note (August 2016): Maps, rich media, and text have been updated to reflect a taxonomic change/split for this species. This species account is still being edited and may contain content from an earlier version of the account.
Oak Titmouse is a common residents of warm, dry woodlands in the western United States, and northwestern and southern Baja California. Until recently, Oak and Juniper titmice were regarded as a single species in the genus Parus: Plain Titmouse (Parus inornatus). A comprehensive analysis of geographic variation in the species complex ( Cicero 1996 ), along with genetic evidence of relationships within the family ( Sheldon et al. 1992 , Slikas et al. 1996 ), has led to their reclassification as sibling species in the genus Baeolophus ( American Ornithologists' Union 1997 ). Although similar in appearance, the 2 species are distinguished by a suite of morphologic, colorimetric, genetic, vocal, and ecologic traits ( Cicero 1996 ).
The Oak Titmouse is found primarily in oak or oak-pine (Quercus-Pinus) woodlands of the Pacific slope. It is sedentary, nests in natural or woodpecker-excavated cavities, and mates for life. Pair bonds form during the first year, and both sexes defend territories year-round. Thus, unlike many other parids, Oak Titmouse generally do not form winter flocks. Clutches typically contain 6–7 unmarked eggs.
The diet is varied, and they are known to cache food. They are highly vocal, and individuals are most commonly recognized by their chatterlike calls which males and females utter throughout the year. Males may sing infrequently during the nonbreeding season, with singing intensity increasing toward spring. Vocalizations are directed primarily toward intraspecific defense of territories.