Anyone who enjoys bird song dreads summer’s end as a bit of an auditory desert. But if you live near California Thrashers, you can take heart. These songsters will actually begin ramping up their voices again in late August.
Slightly larger than a California Scrub-Jay, a California Thrasher features a long, heavy, and distinctly downturned bill; dark eyes; and a lengthy, slightly wilted tail. Except for a whitish throat, the bird appears, to the naked eye, basically dark. A look through optics in good light, though, reveals lovely, subtle coloring: grayish brown above, slightly paler and warmer brown below, a buff-tinged belly and undertail, and a streaky triangular face mask. This thrasher flies reluctantly, usually preferring to scurry for cover with its head down, wings partially opened, and tail raised. Over most of its distribution, it is the only thrasher species although its range almost abuts that of the similar-looking (although pale-eyed) Crissal Thrasher in southeastern California. But really, the bird you’re most likely to confuse with a California Thrasher is the similarly plumaged but smaller and much-smaller-billed California Towhee. If you’re looking at a dirt-colored bird and you’re not thinking, “Wow—look at that bill!” you’re probably not watching a California Thrasher.
Coupled with its sickle-shaped bill and dramatically long tail, the California Thrasher’s exceptionally creative song endow the California Thrasher with the distinction that its overall drab plumage does not. The male vocalizes much of the year, frequently from the highest point available—a tree, a tall shrub, a fencepost—making him easy to spot. His song offers a series of lazy phrases sprinkled with a mix of buzzy, trilled, and harsh-sounding notes as well as calls, alarm notes, and mimicked phrases of other species in the area, each generally repeated two or three times. (Note that a Northern Mockingbird—another talented mimic with an extremely varied song—usually repeats its sweeter-sounding phrases four to seven times.) He sometimes sings two notes simultaneously, thanks to his specialized vocal organ (syrinx). He also incorporates. A permanent resident, he can sing any time of the year; but his songs’ intensity varies through the seasons. He sings more or less continuously from November to June but then quiets as summer progresses. He cranks his tunes back up again starting in mid-August.
Endemic to California and northern Baja, California Thrashers prefer hillside chaparral; but they also inhabit sagebrush, riparian and oak woodlands with brushy understory, and suburban yards and parks with good understory. Common over much of San Diego County, these birds don’t adapt well to urban development; as a result, the only gaps in county distribution lie in the most heavily urbanized areas.
Primarily insectivorous during breeding season, California Thrashers locate insects and other arthropod prey by digging energetically in leaf litter and soft ground with those decurved bills (not with their feet, as towhees or other sparrows do), usually near cover. They can be conspicuously noisy when foraging, vigorously swiping loose duff and leaves aside or even tossing clods and twigs (the eponymous “thrashing”) and then probing with their bills. Thrashers feed extensively on soft fruits (e.g., berries from poison oak, toyon, manzanita, mistletoe) from late summer through winter.
Pairs tend to form long-term relationships, typically raising two broods a year. The female lays her first clutch as early as February or March. The second brood immediately follows the first, with the female often laying the second clutch while the male feeds the dependent young of the first brood. She generally lays three or four eggs; incubation lasts 14 days and the young depart the nest after 12–14 days. Newly fledged kids have well-developed legs but initially fly weakly. By eight days out of the nest, though, their wings have developed and they can fly well. Parents feed the fledglings as long as three weeks after leaving nest.
The California Thrasher’s scientific name is Toxostoma redivivum. The genus name means “bow mouth,” from Greek toxon (“bow”) and stoma (“mouth”), referring to the downcurved bill that the person naming the species thought resembled a strung bow. The species name—redivivum—derives from Latin for “revived.” The species was first described in the 1780s and placed in the genus Promerops (along with sugarbirds from southern Africa). It was not noted again until 1845; at that time, William Gambel placed this bird in the current genus and assigned this species name because the bird had been “rediscovered.” Its common name boasts more obvious roots: “California,” for its restricted range; “thrasher,” referring to its behavior while feeding.
As summer winds down, a hush falls over the avian symphony hall. Yet lurking off-stage, warming up his syrinx, the California Thrasher clears his throat and begins his mixtape aria anew. At the end of this year’s breeding season, he reminds us that the next breeding season lies just over the horizon.