- 0.4–0.7 oz
- Smaller than a Western Bluebird; slightly larger than a Black-throated Gray Warbler.
- Mésange unicolore (French)
- The Oak Titmouse’s species name, inornatus, means “plain,” appropriately for this very drab-plumaged bird. Taxonomists used to lump the Oak Titmouse with the Juniper Titmouse, referring to both as the Plain Titmouse. Though the two sister species look very similar, the Juniper Titmouse sings differently and lives mainly among not oaks but junipers. Their ranges overlap only in extreme northern California.
- In its pursuit of insects and plant materials, the Oak Titmouse forages at a rate of about 40 food-catching attempts every 15 minutes.
- One of the Oak Titmouse’s vocalizations is a peter peter peter song, which is apparently equivalent to the similar song of the Tufted Titmouse. The song’s pattern, of high-frequency notes followed by low-frequency notes, is seen across the titmouse and chickadee family.
- The Oak Titmouse sleeps in cavities or in dense foliage. When roosting in foliage, the titmouse chooses a twig surrounded by dense foliage or an accumulation of dead pine needles, simulating a roost in a cavity.
- The Oak Titmouse mates for life, and pairs defend year-round territories. Most titmice find a mate in their first fall. Those that do not are excluded from territories and must live in marginal habitat until they find a vacancy.
- The oldest Oak Titmouse on record was at least 8 years and 1 month old. It was caught alive by a bird bander in Oregon and released.
Oak Titmice live mostly in warm, open, dry oak or oak-pine woodlands. Many will use scrub oaks or other brush as long as woodlands are nearby. They live in a restricted range, from southwest Oregon to northwest Baja California, with another population in the Cape District of south Baja California. In a few areas they use habitats without oaks. In extreme northern California, Oak Titmice live in western juniper woodlands (the only part of their range where they overlap with the Juniper Titmouse). On San Benito Mountain in central California they live in open pine forests. In the mountains of northwest Baja, they live in pinyon pine woodland. At the eastern edge of their range, they live in pinyon or California juniper mixed with Joshua trees.
The Oak Titmouse eats seeds and other plant materials as well as insects and other invertebrates, particularly in warmer months. It eats acorns, pine seeds, oats, thistle seeds, poison oak berries, oak and willow catkins, leaf buds, galls, berries, and cultivated cherries. Its invertebrate diet includes leafhoppers, treehoppers, plant lice, aphids, scales, caterpillars, beetles, ants, wasps, flies, and spiders. The Oak Titmouse gleans its prey from bark and foliage, usually less than 30 feet off the ground. It uses its stout bill to peck and probe crevices, chip away bark, and pull apart leaf galls, flowers, acorns, curled dead leaves, and lichens in search of prey. It may also forage on the ground itself, taking its food to an elevated perch with good visibility before eating it (or storing it to retrieve later). For large food items, it holds the item against a branch with its foot and pulverizes it with its bill. Occasionally it catches insects out of the air.
- Clutch Size
- 3–9 eggs
- Number of Broods
- 1-2 broods
- Egg Length
- 0.6–0.8 in
- Egg Width
- 0.5–0.6 in
- Incubation Period
- 14–16 days
- Nestling Period
- 16–21 days
- Egg Description
- White, sometimes speckled with a faint reddish brown.
- Condition at Hatching
- Undeveloped and helpless.
The female takes charge of building the nest, taking 4–10 days to finish it. The male accompanies her while she gathers material and he feeds her when she is inside the cavity. Nests are made of grass, moss, hair, and feathers, and may also contain shredded bark, wool, straw, twigs, plant fibers, rope, string, oak blossoms, snakeskin, sycamore seed balls, rootlets, leaves, and wood chips. The nest may be reused in later years, either by the same pair or a different one.
The female selects the nest site, but the male goes with her as she roams across their breeding territory to inspect sites. She chooses a cavity in a tree up to 40 feet off the ground, preferring natural cavities over woodpecker-excavated ones. Sometimes she may partially excavate the nest herself in soft or rotten wood, or further excavate an existing cavity. Occasionally Oak Titmice nest in stumps, fenceposts, pipes, eaves, or holes in riverbanks. They will also use nest boxes.
Oak Titmice flit between branches and trees, flying with a shallow undulating motion. They tend to feed among the woody twigs in the lower canopies of oaks and other trees. They form pair bonds in their first year and mate for life. Both sexes defend territories year-round, meaning they don’t flock in the winter the way many other titmice and relatives do. When defending against an intruding member of its species, the Oak Titmouse raises its crest, quivers its wings, and scolds. Oak Titmice are hunted by mammals, snakes, and other birds, including Western Scrub-Jays, Steller’s Jays, Western Screech-Owls, Northern Pygmy-Owls, and accipiter hawks. Oak Titmice will mob predators, often joining forces with other small birds.
The Oak Titmouse is one of the most common birds in oak woodlands of California, but populations have declined by about 1.4 percent per year between 1966 and 2010, resulting in a cumulative decline of 46 percent, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 500,000 with 89 percent occurring in the U.S. and 11 percent in Mexico. The Oak Titmouse is listed as a U.S.-Canada Stewardship species and rates a 14 out of 20 on the Continental Concern Score. This species is on the 2014 State of the Birds Watch List, which lists species most in danger of extinction without significant conservation action. The decline of this species is linked to the increase in California's population during the twentieth century (from 1.5 million to more than 30 million people), which has increased pressures on oak woodlands from activities such as timber harvesting, clearing for agriculture, and urban and suburban development. An estimated 80 percent of California’s remaining oak woodlands are privately owned, so landowners can play a crucial role in conservation of this unique habitat.