The California Thrasher is endemic to California and Baja California, where it is a resident of chaparral habitats. A noted singer, the California Thrasher sings nearly year-round and can mimic the songs of other bird species.
California Thrashers react very strongly to Western Scrub-Jays, and may even kill them, because jays are capable of eating the eggs or young of the thrashers. At bird feeders, California Thrashers generally dominate mockingbirds, towhees, and sparrows.
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Description of the California Thrasher
The California Thrasher has grayish-brown upperparts and breast, a buffy belly, a long tail, a long and much decurved bill, a black malar stripe, and dark eyes. Length: 12 in. Wingspan: 12 in.
The sexes are similar.
Seasonal change in appearance
The sexes are similar.
Juveniles resemble adults, but have less contrasting colors.
California Thrashers inhabit gardens, parks, and chaparral.
California Thrashers eat insects and berries.
California Thrashers forage primarily on the ground.
The California Thrasher is an endemic, resident species which forms long term pair bonds.
California Thrashers defend territories year-round.
Calls include a “chuk” or “churrup” sound, while the song is a series of harsh, repeated phrases.
The Crissal Thrasher is similar, but their ranges do not overlap.
The California Thrasher’s nest is a cup of twigs lined with finer materials, and is placed low in dense vegetation.
Number: Usually lay 3-4 eggs.
Color: Bluish with darker markings.
Incubation and fledging:
The young hatch at about 14 days, and leave the nest in about another 12-14 days, though continuing to associate with the adults for some time.
Bent Life History of the California Thrasher
Published by the Smithsonian Institution between the 1920s and the 1950s, the Bent life history series of monographs provide an often colorful description of the birds of North America. Arthur Cleveland Bent was the lead author for the series. The Bent series is a great resource and often includes quotes from early American Ornithologists, including Audubon, Townsend, Wilson, Sutton and many others.
Bent Life History for the California Thrasher – the common name and sub-species reflect the nomenclature in use at the time the description was written.
TOXOSTOMA REDIVIVUM REDIVIVUM (Gambel)Contributed by ROBERT S. WOODSHABITS
The California thrasher is appropriately named, as it is one of a number of birds of various families that, while common and widely distributed in California, are almost exclusively confined to that State, with its faunal extension, the northwestern portion of Baja California. The range of the species extends from the western slopes of the Sierra Nevada and the higher mountains of southern California to the Pacific, and from the head of the Sacramento Valley to about latitude 300 in Baja California.
As pointed out by Dr. Joseph Grinnell (1917), it is predominantly a species of the Upper Sonoran Zone, being most abundant along the bases of the mountains, where it ascends the brushy southerly and westerly slopes to an altitude of at least 5,000 feet in the southern part of the State, but never enters the Transition Zone coniferous forests. Its lower limits, however, are less strictly defined, especially toward the south, where it follows the brush-bordered watercourses down into the Lower Sonoran. Dr. Grinnell suggests that a certain degree of atmospheric humidity may also be a requisite for this species, as it fails to follow the Upper Sonoran Zone around the southern end of the Sierra Nevada into apparently suitable territory on the eastern slope of the range.
The California thrasher has occasionally been found nesting on the desert side of the San Gabriel, San Bernardino, and San Jacinto Mountains, in the territory of the crissal and LeConte’s thrashers, but in general both high mountains and deserts constitute effective barriers to its spread. As to its ecological relationships, Dr. Grinnell (1917) says:
The California Thrasher is a habitual forager beneath dense and continuous cover. Furthermore, probably two-thirds of its foraging is done on the ground. In seeking food above ground, as when patronizing cascara bushes, the thrasher rarely mounts to an exposed position, hut only goes as high as is essential to securing the coveted fruits. The bird may be characterized as semi-terrestrial, but always dependent upon vegetational cover; and this cover must be of the chaparral type, open next to the ground, with strongly interlacing branch-work and evergreen leafy canopy close above: not forest under-growth, or close-set, upright stems as in new-growth willow, or matted leafage as In rank-growing annual herbage.
In these favored haunts throughout its range the thrasher is associated with two other birds of rather similar coloration, the brown towhee and the wren-tit. Like the towhee, the thrasher holds no prejudice against civilization but becomes a common and by no means shy dooryard resident of the foothill towns.
In comparing the species of this genus, William L. Engels (1940) writes: “The California * * * thrasher appears to have few characters in common with the brown thrasher: the bill is very long and markedly decurved, sicklelike; the bird’s upper parts are grayish brown and the underparts somewhat lighter in color, but without the dark streaks so distinctive of the brown thrasher. The migratory brown thrasher, in its daily rounds, progresses predominantly by flight; the nonmigratory California thrasher is a swift and skillful runner and makes little use of its wings in moving about. Other species of the genus are intermediate in various respects between these two extremes.”
He also finds that the three species occurring regularly in California, redivivum, lecontei, and dorsale, form a group distinguished from the more eastern members of the genus not only in their plain coloration and longer, more curved bills, but also in their reluctant flight and their strong digging propensities. Furthermore, when on the ground, according to Mr. Engels, “the tail is held low in rufum, bendirei and curvirostre; it is carried up at a sharp angle in redivivum, dorsale and lecontei.”
The typical form of the California thrasher occupies the southern portion of the territory, as far north as Monterey and Placer Counties. It differs from the northern subspecies in the more grayish brown of the general plumage and the white rather than buffy color of the throat.
Nesting: The nesting habits of the California thrasher offer little of divergence from those of others of its genus and family, aside from the notable length of its breeding season. The birds apparently remain mated throughout the year, and Mrs. Grace Tompkins Sargent (1940) mentions one brood having been brought off in Pasadena during the month of November 1935. Other occupied nests have been reported for each subsequent month up to at least July. February and March, however, are more usual months for the opening of the nesting season, the raising of the second brood often lasting well into summer.
The nests are usually placed within a few feet of the ground, well inside a large bush or scrubby tree. Dense masses of foliage are avoided, but the sites are usually well screened from outside view. In its construction the nest closely resembles that of mockingbirds building in the same locality, except of its slightly larger size and coarser materials, in proportion to the sizes of the birds. The foundation and body of the structure are composed of stiff, rough twigs, with a lining of rootlets, fibers, grasses, or other flexible material.
When incubating or brooding, the thrashers often show little fear when approached, and W. Leon Dawson (1923) tells of picking up one of the birds and turning it around on its nest so that it would face his camera! They are, nevertheless, cautious in their approach to the nest, as Mr. Engels (1940) mentions: “Of two pairs of California thrashers whose nesting activities I observed, I never saw a bird approach the nest in any way but through the bush, working up from the base after coming to it on the ground. One nest was about 4 feet above ground in a bush, and the birds here often left in the same manner in which they had come—except when frightened off, when they flew down to the ground.” By this habit of approaching the nest from the ground, and by the reluctance of the sitting bird to be flushed, the thrasher guards well the secret of its nesting site.
Eggs: [AUTHOR’S note: The California thrasher lays two to four eggs to a set, apparently oftener three than four and only rarely two. These are mostly ovate, with variations toward elliptical-ovate or short-ovate. They are only slightly glossy. The ground color is “Nile blue,” “pale Nile blue,” or even paler blue. They are more or less evenly covered with small spots, flecks, or fine dots of pale browns; these are often very faint and sometimes much scattered; they are very rarely conspicuously spotted, or even dotted with darker browns.
The measurements of 50 eggs in the United States National Museum average 30.1 by 21.2 millimeters; the eggs showing the four extremes measure 3441 by 21.3, 30.5 by 22.9, 26.4 by 20.8, and 30.9 by 19.8 millimeters.]
Young: According to Mrs. Irene G. Wheelock (1904), “both sexes assist in the construction of the bulky nest, and both brood on the eggs. In 14 days the naked pink young emerge from the shells and are fed by regurgitation for 4 days, or until their eyes open.” And from the same source: “The young thrashers leave the nest when 12 to 14 days old, but are fed by the adults for some time after. I have found the male caring for a fully fledged brood, while his mate was sitting on a nestful of eggs; and after this second series were hatched, he at once began to feed them as faithfully as he had fed the first.”
In refutation of the theory that “a parent bird is moved to feed its young only by that young bird’s opening its mouth,” Ernest I. Dyer (1939) cited the behavior of this species, stating that “in the case of every one of the 15 or 20 nests of the California Thrasher which [the writer] has had under observation at his home, at ‘reading distance,’ there have been innumerable instances of one or the other of the parents’ persistently trying to induce a totally unresponsive chick, by cluckings and bill-proddings, to open its mouth to receive food.”
The bills of the nestlings are proportionately shorter and much less curved than those of the adults. After the young appear fully mature in other respects, their bills are still noticeably short. Since the maximum sicklelike development of the bill is seen in comparatively few individuals, it might be surmised that the growth of this member continues through a part, at least, of the adult life.
Plumages: [AUTHOR’S NOTE: According to Ridgway (1907), the young are “essentially like adults but browner above, with larger wing-coverts and tertials margined terminally with lighter cinnamon-brownish, the rectrices more or less rusty brownish terminally; chest less grayish (more brownish), sometimes only slightly different from general color of under parts.”
The postjuvenal molt of young birds occurs mainly in July. The late-summer molt of the thrasher is perhaps more noticeable than that of any other California land bird. In this it contrasts strongly with the mockingbird, which is seldom seen in a disheveled state. During this period following the end of the nesting season, individuals can always be seen in smooth, neat plumage, and others in a very ragged condition. The latter birds show no inclination to seek seclusion, but pursue their usual activities.]
Food: In an examination of 82 stomachs of this species, Prof. F. E. L. Beal (1907) found vegetable food to exceed animal in the ratio of 59 to 41. Carabidae constituted 3.8 percent, other beetles 6 percent, the most numerous being darkling beetles (Tenebrionidae) and May beetles (Scarabaeidae). “But very few weevils or other species that live on trees or foliage were found. Of all the insects, Hymenoptera are the most abundant, as they are also the most constant element of the thrasher’s food. About half of these are ants, the rest wasps and bees. * * * Together they make up something more than 12 percent of the food of the year. Two specimens of worker honey-bees (Apis mellifera) were found in one stomach.” Caterpillars, cocoons, and moths amounted to 8 percent, mostly eaten during winter, probably while hibernating; spiders and myriapods formed 6 percent.
Of the vegetable food, Prof. Beal found 18 percent represented by fruit, “probably not of much value.” Seeds of blackberries or raspberries, elderberry, cascara, and manzanita were present. The seeds of poison oak and other species of Rhus formed 14 percent. “They were not found in many stomachs, but appear to be eaten in considerable quantities when eaten at all.” The miscellaneous part of the vegetable food, amounting to 26 percent, consisted of mast, weed seed, galls, and rubbish. Professor Beal concludes: “It is not probable that the California thrasher will ever become of special economic interest unless under very exceptional circumstances. In the meantime it performs its part in the great work of reducing the vast numbers of insects.”
The thrashers will eat figs and cactus fruit, such as that of the cultivated “spineless” Opuntia, but as a rule they show little interest in any kind of fruit too large to be swallowed whole; obviously the shape of the bill is not well adapted to biting. They are very fond of grapes, especially the small seedless varieties, and display great persistence in finding openings through any sort of net that may be put over them. They relish also the berrylike grains of the pomegranate, available to them after the splitting of the hard rind. As with many other birds, offerings of crumbs and table scraps seem to be most acceptable in cool weather, or when there are families to be fed. At times California thrashers will visit a feeding-table regularly and eat quantities of dry bread crumbs, a food which the mockingbird only occasionally deigns to notice; in general, however, the food preferences of the two species are similar.
Behavior: Prominent among the characteristics of this species is its adaptation and preference for the terrestrial mode of life. On the ground it is swift, efficient, and at ease; but when forced to take to the air, its jerky flight, accomplished by labored beating of its short wings, and with awkwardly drooping head and tail, offers the greatest possible contrast to the graceful buoyancy of its relative and frequent neighbor the mockingbird. The thrasher’s usual gait is a brisk run, even when proceeding a very short distance. In moving only a step or two, it may either walk or hop. While the bird is running, the tail is tilted upward, but when perching it is held in line with the body or drooping slightly.
The California thrasher, in its native haunts, has frequently been referred to as a shy bird; perhaps, however, this is mainly due to the nature of its usual surroundings, which make keeping out of sight an easy matter. In our dooryards it is one of the least timorous of birds, paying not the slightest attention to any unusual paraphernalia, such as a camera and tripod, and showing no aversion to lawns and other open spaces. In its attitude toward other birds it is bold and confident, and the California jay, of equal size, deems it prudent to defer to the thrasher at the feeding-table. Among themselves the thrashers are not quarrelsome; sometimes they are seen chasing one another about on the ground, but this often seems to be in a spirit of play.
In its territory the thrasher is unique in its method of foraging. Most of its animal food is obtained by raking away fallen leaves or by digging in the soil. In the words of Dr. Grinnell (1917), “The bird’s most conspicuous structural feature, the long curved bill, is used to whisk aside the litter, and also to dig, pick-fashion, into soft earth where insects lie concealed. Ground much frequented by Thrashers shows numerous little pits in the soil surface, less than an inch deep, steep on one side and with a little heap of earth piled up on the opposite side.” In the Point Lobos Reserve, according to Grinnell and Linsdale (1936), “the most suitable foraging situation was the accumulation of leaf litter beneath the ceanothus bushes.” Flower beds also are favored resorts, and in their entirely laudable search for cutworms and other pests, the birds are apt to annoy gardeners by digging up newly planted bulbs and seeds. On the technique of digging, Mr. Engels (1940) writes:
The food which it obtains from the ground and surface debris beneath the chaparral cover is procured entirely by means of the long, curved bill. The feet are never employed for scratching, but ground spiders, grubs, and crickets are dug out of the ground; the curved bill is struck into the ground with rapid strokes of the head and neck, and the dirt “hooked” back and out with a powerful pull of the neck. Side-to-side sweeps of the bill are also frequent in the digging operation, but most of the dirt is thrown backward. Rather large objects may be thus moved; I once saw a California thrasher toss a clod of dirt calf the size of my fist a distance of nearly 2 feet.
The bill is not always kept closed during the digging operation; the mandibles are frequently separated by a few millimeters, being then driven into the ground like a two-pronged fork rather than a single pick. This was seen more often in the “hooks” and “pulls” than in the “lateral sweeps”. Once an opening is made in the ground surface, many direct downthrusts or pokes are made. When digging, the bird frequently stops, cocks its head far to one side, bringing one eye to bear directly on the work, and seems to peer into the excavation.
* * * All parts of the body except the wings are brought into play in this operation, each contributing its share to the sum of the forces which produce the powerful digging strokes and the return of the body to an easy, balanced position.
That the use of the bill for opening nuts may involve a possible hazard is indicated by a manuscript note from Mrs. Amelia S. Allen, of Berkeley: “One came to the tray with a hazelnut stuck on its beak. It tried to knock it off by striking it against the tray; then flew to the ground and pecked; then to a branch where it rubbed the shell against its foot. It disappeared in the brush with the shell still on its beak.”
Though most of the habitat of this species is deficient in water, the thrashers make frequent use of it in hot weather if it is provided. They appear to drink very copiously, but it may be merely that the shape of the bill makes drinking a tedious process. In view of the fact that wasps are reported to make up a considerable portion of their diet, it is strange to note the almost ludicrous attitude of alarm induced by the arrival of one of these insects at a bird bath where a thrasher is drinking. In cooler weather, water is utilized for bathing, which is done in a practiced and thorough manner.
Under only one circumstance does the California thrasher forget its affinity for the earth and its inclination to remain as close to it as possible. When it feels the urge to sing it seeks the most conspicuous position available, the topmost twig of a large bush or small tree. The song ended, it spreads its wings and glides back to earth. At no time does it share the fondness of many other ground-foraging birds for the roofs of buildings.
Voice: The California thrasher is not ordinarily a voluble bird, nor are its call notes varied. As it goes about its usual business it occasionally utters a flat and unmusical chack, or more rarely a harsh note of alarm. It is only when it mounts to the top of a bush or tree and pours out its rich song that its vocal abilities may be appreciated.
At its best, the song of the thrasher is one of the finest of bird songs, probably less fluent than that of the mockingbird, but deeper and richer. Its quality varies greatly, probably both with the ability of the individual and the mood of the singer. Mrs. Sargent (1940) found that a female which she watched for more than a year also sang on certain occasions, sometimes “loudly and sweetly,” and says that in January the mated pair once sang together for about 15 minutes and for shorter periods at other times. While winter and early spring seem to be the seasons of greatest vocal activity, the thrasher’s song may be heard intermittently at almost any time of year.
Like the mockingbird, the California thrasher often interpolates into its song the utterances of other birds, including, according to John Van Denburgh (1899), the flicker, house finch, quail, goldfinch, and black-headed grosbeak. Ornithologists differ in their estimates of the thrasher’s ability as a mimic, most of them ranking it below the mockingbird. My experience, however, has been the reverse, and it seems probable that there are individuals in both species that are outstandingly proficient. One midwinter day I was surprised to hear the unmistakable buglelike notes of Bullock’s oriole, a summer visitant, and traced them to a California thrasher singing on the top of a bush. Again, late in summer, the song of a thrasher contained notes resembling those of the robin, a winter visitor here. These incidents seem to indicate that the thrasher’s memory is at least several months long.
Another striking demonstration of mimicry, perhaps by the same thrasher, was the reproduction of the short howl or wail of the coyote. Such was the ventriloquial effect and the perfection of the rendition that even as I watched the bird singing on the top of a nearby bush, it would have been difficult to believe that I was not actually hearing a coyote in the distance had not the wails fitted perfectly between the phrases of the song.
Mrs. Allen (MS.) has noted the following imitations by thrashers at Berkeley: long-tailed chat, red-tailed hawk, robin, ruby-crowned kinglet, olive-sided flycatcher, titmouse, house wren, willow goldfinch, California jay, quail, purple finch, European blackbird, frog, and postman’s whistle. Most of these were recorded in September. In eight different years she found the song period marking the completion of the molt to begin in August; in 11 years the starting of territorial song ranged from December 21 to February 22.
Field marks: The California thrasher’s long, decurved bill is sufficient to distinguish it from any other bird ordinarily seen within its territory. When its bill is not visible, it might be mistaken for a brown towhee, but the tail is appreciably longer and is often tilted up. In and around the passes leading from the Pacific slope to the desert, the range of this species is said to slightly overlap the territories of the crissal and LeConte’s thrashers. From LeConte’s the California thrasher is distinguished by its darker color and somewhat longer, more curved bill; with the crissal it agrees rather closely in size, coloring, and shape of bill, the identification being based principally on the color of the under tail coverts, cinnamon in the California thrasher, cinnamon rufous in the crissal. In the California and LeConte’s thrashers, the iris is always brown; in the crissal it is usually represented as light yellow, though Ridgway (1907) described it as brown; in other species of the genus the iris is yellow or orange.
Enemies: Hearing a succession of frenzied shrieks in the yard one day, I hastened out to find a thrasher in the grip of a sharp-shinned hawk. Upon seeing me the hawk immediately flew away, leaving its intended victim apparently little the worse for the encounter. In this instance the thrasher’s vocal chords had proved its best defensive weapon.
From the nature of its habits the thrasher would seem to be especially vulnerable to terrestrial enemies, but it is undoubtedly a bird of more than average sagacity, and I have seen no indication that many of the adults fall victim to cats or other prowlers. Because of the scant height at which the nest is usually placed, there must be a considerable loss from semiterrestrial nest-robbers, such as skunks, banded racers, and perhaps alligator lizards, as well as from the California jay.
Dr. Grinnell (1917) surmises that in view of the thrasher’s dull brown coloration, swiftness of foot, and poor flight, the chaparral cover may be quite as valuable in its protective effect as it is in furnishing a suitable foraging ground.
Range: California and northwestern Baja California; nonmigratory.
The California thrasher is found north in California to extreme southern Humboldt County (Thorn); central Trinity County (Hayfork); Shasta County (Baird); and Tehama County (Manton). East to Tehama County (Manton); the western slope of the Sierra Nevada (Grass Valley, Placerville, Murphy, El Portal, and Walker Pass); western San Bernardino County (Hesperia and Redlands); Riverside County (Palm Springs); eastern San Diego County (Jacumba); and northwestern Baja California (Hanson Laguna, Sierra San Pedro Mártir, and San Fernando). South to northwestern Baja California (San Fernando and Rosario). West to the Pacific Ocean in Baja California (Rosario, San Quintin, and Ensenada); and California (San Diego, Los Angeles, Santa Barbara, Monterey, Nicasic, Ukiah, Cummings, and Thorn).
The range as given for the entire species is divided into two subspecies. The Sonoma thrasher (T. r. sonomae) occurs in the northern part of the range south to Eldorado, San Joaquin, and Santa Cruz Counties; the California thrasher (T. r. redivivum) occupies the range from there southward.
Egg dates: California: 132 records, December 15 to June 27; 72 records, March 20 to May 8, indicating the height of the season.
TOXOSTOMA REDIVIVUM SONOMAE Grinnell
This northern race of the well known California thrasher is described by Dr. Joseph Grinnell (1915) as “similar to T. r. redivivum, but size slightly greater and back, chest and sides less ‘warm’ in tone of brown; similar to T. r. pasadenense, but size, especially of foot, greater, and coloration throughout darker, less ashy.”
He says that it is a “fairly common resident of the Upper Sonoran zone around the upper end of the Sacramento Valley and thence west through the inner coast ranges north of San Francisco Bay.” It probably intergrades with the more southern race in the vicinity of Placer County. It has been recorded from Shasta, Mann, Mendocino, and Solano Counties.
I cannot find in the literature, or in contributed notes, anything to indicate that this thrasher differs at all in its habits from the closely related California thrasher, which has been so well treated by Mr. Woods.
In the Lassen Peak region, Grinnell, Dixon, and Linsdale (1930) found this thrasher living mainly in the scrub-oak chaparral. One nest was found in an isolated clump of buckbrush, and other nests were seen in clumps of scrub oaks.
The eggs are indistinguishable from those of the California thrasher. The measurements of 25 eggs average 31.2 by 21.5 millimeters; the eggs showing the four extremes measure 33.1 by 22.2, 31.9 by 22.7,29.2 by 21.2, and 31.3 by 19.5 millimeters.