T. r. sonomae is found from Trinity and adjoining counties in northern California southwards to the range of the nominate subspecies.

[3] The California thrasher has a distinct foraging behavior, often seeking food under dense and continuous cover.

The California thrasher forages mostly on the ground, by digging and sweeping leaf litter and soil with its bill.

[6][3] The California thrasher has a distinct foraging behavior characterized by its habit of searching for food beneath dense and continuous cover.

The bird's choice of foraging grounds reflects its adaptation to the dense shrubbery and undergrowth common in its habitat.

The California thrasher's core breeding season spans from February into July, though it often begins in January.

[3] Both sexes of the California thrasher engage in singing, typically from elevated and exposed perches, delivering "vigorous and 'cheerful' phrases variously repeated."

This intricate understanding of song structure is believed to play a crucial role in territorial defense.

This bird's vocalization is not only rich but also unique in its sensitivity to song syntax, allowing it to communicate and defend its territory effectively.

[7] The California thrasher occupies a unique ecological niche, characterized by its strong association with dense undergrowth and shrubbery, which provides it with ample foraging opportunities and shelter.

Its niche relationships also extend to its interactions with other bird species, forming a distinct part of the Californian fauna.

[5] The California thrasher's interactions with other bird species and wildlife within its habitat contribute to the ecological dynamics of the regions it inhabits.