About the Oak Titmouse
Once classified with the juniper titmouse as a subspecies of the aptly named plain titmouse, the oak titmouse is easily separable from other timice species except the juniper. Its lack of field marks is, ironically, an important field mark. Polytypic. Length 5".
The bird is a drab brownish or grayish brown color overall, but is paler below. It has a short crest.
Four subspecies, one restricted to Baja California; variation is weak and clinal. The northernmost subspecies, inornatus, from Oregon to south-central California, has medium brownish gray or olive-brown upperparts, pale gray underparts with pale brown tinge on flanks, and a short bill. The affabilis found in southwestern California is notably larger, has darker gray-brown or olive-brown upperparts, flanks washed in dusky brown, and a longer bill. The mohavensis, restricted to the Little San Bernardino Mountains in San Bernardino and Riverside Counties, is smaller, paler, and grayer than the affabilis.
The closely related juniper titmouse is slightly larger, paler, and grayer, but similarly plain. The two are best separated by range; they are sedentary and are sympatric only in a small area of northern California. No other titmouse poses a problem; they can be identified by conspicuous differences in plumage on head or flanks.
Call: a hoarse tsick-a-deer. Song: a series of clear, whistled sets of alternating high and low notes, such as peter peter peter or teedle-ee teedle-ee, with many variations.
Status and Distribution
Common. Year-round: primarily oak and pine-oak woodlands on the Pacific slope. Vagrant: casually reported east of its usual limits in California.
Declining in California because of losses in its preferred oak habitat, primarily by encroaching suburban and agricultural development, although disease could become a new threat with the appearance of Sudden Oak Death Syndrome.
—From the National Geographic book Complete Birds of North America, 2006