The Sage Thrasher is smaller in size than its thrasher relatives, but occurs over a fairly broad range in the western U.S., where it migrates short distances from breeding to wintering ranges and back. When not migrating, Sage Thrashers spend much more time walking or running than flying.
Sage Thrashers rapidly remove Brown-headed Cowbird eggs from their nests, so it is difficult for researchers to know how often cowbirds choose to parasitize them. Loss of sagebrush habitat through conversion to planted wheatgrass or cheatgrass renders habitat unsuitable for Sage Thrashers.
Length: 8 inches
Wing span: 12 inches
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Description of the Sage Thrasher
The Sage Thrasher has brownish-gray upperparts, pale underparts with dark streaks, two white wing bars, and white-tipped corners to the tail visible in flight.
Seasonal change in appearance
Juveniles resemble adults.
Sage Thrashers inhabit sagebrush, and occasionally other brushy habitats.
Sage Thrashers eat insects and berries, especially those of junipers and Russian olives.
Sage Thrashers forage on the ground, as well as in trees or shrubs to pick berries.
Sage Thrashers breed from southwestern-most Canada south across most of the western U.S. They retreat from northern areas to winter in the southwestern U.S. and Mexico. The population has declined where sagebrush habitat has been lost or altered.
Sage Thrashers are persistent singers during morning hours of the breeding season.
Though a bird of the west, strays are sometimes found well east of the breeding range during the fall.
The song is a long series of warbled phrases that vary in speed. Calls include a “chup” and a “churr.”
- Northern Mockingbirds lack streaking on the breast, and have grayer upperparts.
The Sage Thrasher’s nest is a bulky cup of twigs, leaves and grass and lined with finer materials. It is placed in sagebrush or another low bush.
Number: Usually lay 3-5 eggs.
Color: Greenish-blue with darker markings.
Incubation and fledging:
The young hatch at about 13-17 days and fledge at about 11-14 days, though remaining dependent on the adults for some time.
Bent Life History of the Sage 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 Sage Thrasher – the common name and sub-species reflect the nomenclature in use at the time the description was written.
OREOSCOPTES MONTANUS (Townsend)HABITS
The above scientific name and the old common name, mountain mockingbird, are both misnomers, as this is not a mountain bird and is not a mocker. But sage thrasher is a most appropriate name, for it designates the bird’s habitat and its relationship to the true thrashers. It is the characteristic bird of the vast sagebrush plains, and its distribution is limited almost entirely to the semiarid regions where immense areas are clothed with practically nothing but a waving sea of pale, gray-green sage (Artemisia tridentata). Only the great sagehen, now rapidly disappearing, seems to show such partiality for the sagebrush plains. Though confined mainly to the valleys and mesas, this thrasher extends its range in many places up into the foothills, where the sage gives way to other bushes, junipers and mahogany woods, up to 4,000 feet or even 6,000 feet at some places; this is as near as it comes to being a mountain bird.
The 1931 Check-list gives its range as north to southern British Columbia and central Montana. It has evidently extended its range more or less irregularly during the past ten years. We did not record it in southern Saskatchewan in either 1905 or 1906, but Laurence B. Potter, of Eastend, of the same general region in which we worked, has sent me several notes on its occurrence there from 1933 to 1939. He says: “Sage thrashers made their first known appearance in this southern part of Saskatchewan during the long period of drought, lately ended, and the first specimen was secured in 1933. Rather unexpectedly, it has continued to migrate north since the wet seasons have set in. The sage thrasher is generally associated with the hot, arid plains, and it seemed strange to find it singing lustily on a cold, wet morning, as on May 8, 1938.” He wrote to me on September 23, 1934, that his friend Charles F. Holmes took a breeding male in 1933 and the next year shot a breeding female and found a nest with eggs. On June 12, 1934, Fred Bard found a nest with a set of five eggs and took both birds; later on he found two more nesting pairs. The thrashers came there quite early in May in 1938 and 1939. Whether this is to be a permanent extension of the breeding range remains to be seen.
Courtship: The first mention of the courtship activities of the sage thrasher is from the notebook of Robert Ridgway, dated April 9, 1868, at Carson City, Nev. Dr. Elliott Coues (1878) quotes from it as follows: “The Sage Thrasher is now one of the most common birds in this vicinity. To-day a great many were noticed among the brush-heaps in the city cemetery. Its manners during the pairing season are peculiar. The males, as they flew before us, were observed to keep up a peculiar tremor or fluttering of the wings, warbling as they flew, and upon alighting (generally upon the fence or a bush), raised the wings over the back, with elbows together, quivering with joy as they sang.”
Ralph Hoffmann (1927) gives this slightly different account of it: “In April and May when the birds are mating, the male Thrasher gives vent to his ardor, not by mounting in the air like many ground birds, but by flying in a somewhat clownish zigzag low over the sage. At the end of this flight the bird lights with wings upraised and flutters them for an instant.”
Nesting: Mr. Ridgway’s notes contain tile first description of the nest of this thrasher that I can find. The sagebushes in the cemetery had been pulled up and piled in a heap; one of the nests was so well hidden in one of these brush heaps that much of it had to be removed before the nest could be seen. Other nests were found in sagebushes on the open plain, but also well concealed.
An early description of an interesting nest is given by Henry W. Henshaw (1875):
Its nest, a bulky and inartistic structure of coarse twigs, lined with grasses and fine rootlets, is sometimes placed in a sage shrub; but more often the bird selects one of the higher bushes, which, armed with sharp, stiff thorns, serves as an admirably secure platform for the clumsy nest, and affords additional security from its winged and four-footed enemies. A nest, which I examined near Fort Garland, was thus placed, and some 8 inches above it was a device, which, though it may have been the result of mere accident, certainly seemed to me to bear in the method of its construction, the evidences of design, and, if the supposition be true, would argue for the designers no small degree of intelligence. This was a platform of twigs, so placed as to screen the setting bird from the rays of the almost tropical sun. The material of which it was composed was precisely similar to that used in the construction of the nest, and it bad been made at about the same time.
Mrs. Bailey (1928) says that, in New Mexico, the nest may be on the ground or in low bushes, “especially sagebrush; bulky, made largely of coarse plant stems, twigs of sagebrush and greasewood, dry sage shreds and sage bark; lined with fine rootlets and sometimes hair and fur.”
In southwestern Colorado, M. French Gilman (1907) found six nests, four of which were in sage and two in greasewood bushes, all 2 to 2½ feet from the ground. One of these had “a distinct arch or platform of dry twigs just above it.” This was probably similar to that described by Henshaw. Dr. Jean M. Linsdale (1938) reports some five nests found in Nevada; two of these were in sagebrush, one in rabbitbrush, one in a greasewood, and one in a horsebrush (Tetradymia); these were all very low nests, ranging from 5 inches to 2 feet above ground, only one above 1 foot. There is a set of eggs in the F. W. Braund collection from New Mexico that came from a nest 2 feet up in a juniper. There are two sets in my collection that came from Utah; the nests were in greasewood bushes and were lined with sheep wool and horsehair.
Eggs: The usual set for the sage thrasher consists of four or five eggs; six eggs are found occasionally and seven have been recorded by Gilman (1907). The average shape is ovate, with variations toward short-ovate or elongate-ovate. They are often quite glossy. They have been said to resemble mockingbirds’ eggs, but they can generally be recognized by the deeper and richer colors. The ground color is a deep, rich blue, or greenish blue, sometimes almost as dark as catbirds’ eggs and sometimes almost as pale as the darker shades of mockingbirds’ eggs, “Nile blue” or “lumiere blue.” They are boldly spotted with large well-defined spots or small blotches, which are not confluent and are sometimes elongated. These markings are usually in the darker shades of rich brown, or reddish brown, such as “chestnut” or “chestnut-brown”; but sometimes the markings are in paler shades, such as “cinnamon-rufous” or “vinaceous-tawny”; sometimes there are a few shell markings of “plumbeous.”
The measurements of 50 eggs in the United States National Museum average 24.8 by 18.0 millimeters; the eggs showing the four extremes measure 29.5 by 19.3 and 22.6 by 17.3 millimeters.
Young: The period of incubation does not seem to have been determined for this species. Apparently both sexes incubate the eggs, for Dr. Walter P. Taylor (1912) says that “one of the birds frightened from a nest proved to be a male, indicating that the male takes part in incubation.” Probably two broods are sometimes raised in a season, but perhaps not regularly.
Plumages: Dr. Linsdale (1938) describes three small young as “covered with tracts of blackish down.” I have not seen any small young, but Mr. Ridgway (1907) says that, in the juvenal plumage, the upper parts are “light grayish brown (decidedly browner than in summer adults), the pileum, back, scapulars, and rump rather broadly streaked with much darker grayish brown; streaks on under parts less sharply defined than in adults.”
The postnuptial molt of adults occurs in August and September and is complete. In fresh fall plumage, the upper parts are grayer than in spring, the tertials are margined terminally with white, and the mmderparts are washed with buff.
Food: The examination of 10 stomachs of the sage thrasher by E. R. Kalmbach (1914) showed that, where the sagebrush areas approach the borders of alfalfa fields, this bird makes itself useful by destroying alfalfa weevils. In bulk, this weevil—
formed about an eighth of the food and was present in 7 of the stomachs. The best work appeared to be done In June, when the insect was eaten at the rate of 3 adults and 6 larvae per bird. One bird had eaten 3 adults and at least 34 larvae, which composed 44 percent of the stomach contents.
Ground beetles were present in all but two of the stomachs examined and formed about 30 percent of the food in June and a lesser amount in April and July. These beetles and a trace of an ant formed the entire contents of one stomach. Darkling beetles of the genera Blapstinus and Eleodes also were frequently eaten, composing a fifth of the food. Hymenoptera, spiders, and caterpillars were other important ingredients. The only vegetable food was a quantity of currants found in one stomach.
Ira La Rivers (1941) gives the sage thrasher credit for being one of the three species that “fed most destructfully” on the Mormon cricket (Anabrus simplex). “Eggs as well as adults were consumed. From my observations, the thrasher played nearly as important a role in the destruction of cricket egg-beds as did the more conspicuous Western Meadowlark. * * * The cricket, actually a long-horned grasshopper, yearly causes damage in Elko, Eureka, Lander, and Humboldt counties, Nevada, by destroying large quantities of range and field forage, crops, and garden stuffs.” He found this thrasher feeding not only on the migrating crickets, in company with mice and shrews, “but also digging up crickets from partly-finished wasp burrows. One individual was surprised in the act of eating a black wasp (Chiorion laeviventris) which had been left by a marauding shrew.”
Mrs. Bailey (1928) says that it also eats locusts, and gives one record of 62 percent grasshoppers. In a considerable tract of gooseberry brush, Dr. Taylor (1912) noted that “hundreds of sage thrashers, in company with large numbers of Brewer sparrows, green-tailed towhees, and fox sparrows, were feeding on the berries.”
Mr. Dawson (1923) writes: “At the close of the season, or when the young are able to fly well, the birds, all absolutely silent now, resort in numbers to the hillside springs and brushy draws to feed on berries, —wild currants, wild gooseberries, and to lesser extent, service berries. This fondness for small fruit has betrayed the birds into conspicuous mischief in the case of isolated ranches and pioneer reclamation projects. Almost devoid of fear, the birds troup into the gardens in late July and August to strip the currant bushes or blackberries, and later the grapevines.”
Clarence Hamilton Kennedy (1911) reports serious damage to small fruits and grapes on his ranch in the Yakima Valley, Wash.:
During the latter half of May, families of Sage Thrashers drift down into the irrigated ranches and begin their season of fruit-eating with the black-cap raspberrIes, which are then beginning to ripen. * * * During the entire summer’s observation I have heard no call of any kind and on hut two occasions during this period have I heard a short burst of song. Their shyness also leaves them. They become as approachable as Robins in an eastern dooryard. They will sit and without fear eat berries within a few feet of pickers.
Immediately following the raspberries come the blackberries. Both are devoured with equal readiness. Sour red berries are eaten as readily as the riper black ones. The berries are eaten whole and because of their size many of those picked off fall to the ground and are lost. After the blackberry season there is a period of 2 or 3 weeks when no small fruits are ripe. During this time the Thrashers stay about the ranches but content themselves with an insect diet.
At the end of this interim, the latter part of July, the early grapes begin to color. At first they pass unnoticed hut by the time one-half of the clusters are purple the Thrashers have commenced to peck them. Usually they break the skin and sip the Juice but occasionally a grape is eaten whole. Alter the feeding on grapes commences the vineyard is never free from Thrashers, which fly up from the vines to near posts and silently watch any intruder. * * *
On this ranch there are 140 vines of Campbell’s Early. The actual loss in weight of grapes through bird damage was 25 percent, but the loss in profits was not less than 50 percent because of the large item of labor in trimming damaged clusters, and the loss in fancy value through the unattractive appearance of the trimmed bunches.
Dr. George F. Knowlton writes to me “During the past several years I have collected 24 sage thrashers in the Snowville area of Box Elder County, Utah. Examination of the stomach contents revealed 21 to contain a total of 65 grasshoppers, 1 field cricket, and 1 snowy tree cricket. One dragonfly was contained. Eighty-six Hemiptera in the stomachs included 54 adult and 13 nymphal false chinch bugs, 9 minds, and 3 pentatomids. The 20 Homoptera included 7 beet leafhoppers and 8 psyllids. The 40 Coleoptera were made up of 5 alfalfa weevils, 1 clover leaf weevil, 2 click beetles, and representatives of various other families. There also were contained 2 larval Lepidoptera, 7 Diptera, 41 Hymenoptera of which 35 were ants, besides 2 spiders and 35 seeds, most of these being black-currant seeds. Many of the birds were taken along a one-eighth-mile fencerow of black currants, very attractive to birds of many species.”
Behavior: The sage thrasher may have been called the mountain mockingbird, or the sage mockingbird, because it impressed some of the early observers with its resemblance to that famous songster in some of its mannerisms. It uses its tail in much the same manner as the mocker, frequently raising it rapidly and then lowering it slowly while perched on a post or the top of a bush, moving its head nervously from side to side as it views the intruder. Again, while running on the ground, the tail is held high and daintily as the mocking bird is wont to do; its pose and flight are also suggestive of the relationship. But its terrestrial habits mark it as a thrasher, for it much prefers running to flying; it runs on the ground much like a robin, when not frightened; when alarmed, it is apt to dash thrasherlike into a bush and escape by running away under cover, or by low flight close to the ground, disappearing among the bushes and perhaps showing itself again on some distant bushtop.
On its breeding grounds it is rather shy and often difficult to approach, but it is tame enough about the ranches and gardens, where it comes in summer and fall in search of berries and grapes and where it is fairly bold and fearless. Mr. Potter writes to me from Saskatchewan: “The sage thrasher, according to the books, is a shy bird, but I have found it, like the brown thrasher, a mixture of shyness and boldness, or rather confidence. In 1937 I watched a thrasher singing on the top branch of a dead willow, about 10 feet from the ground. I stole up by degrees in full view until I was hardly 20 feet away and stood there watching it for some time.”
Cottam, Williams, and Sooter (1942) timed the flight speed of the sage thrasher in Oregon and Utah by comparing it with the speed of an automobile; their four records showed speeds of 22, 25, 28, and 29 miles an hour.
Voice: To appreciate fully the song of the sage thrasher, the poet of the lonesome sagebrush plain, one should visit him in his haunts in the gray of early dawn, before the chilly mists of night have lifted from the sea of gray-green billows that clothe the mesa farther than one can see in the still dim light of the coming day. As the veil lifts with the rising sun, the mists roll away, the shadowy bushes take definite form, the vast plain is spread out before us in all its soft colors, and, scarcely visible in the distance, a gray-brown bird mounts to the top of a tall sage and pours out a flood of glorious music, a morning hymn of joy and thanksgiving for the coming warmth of day. It may not be the finest bird song that we have ever heard, perhaps not equal to that of the mockingbird, or even that of some other thrashers, but in the solitude of such drab surroundings it is soul-filling, satisfying, and inspiring.
In pure sweetness of tone the song is fully equal to that of the mockingbird; it is full of melody and tenderness. It is suggestive of the song of the solitaire, but is more like that of the brown thrasher, with the frequent repetition of the phrases but without the pauses between them. Like this thrasher, it sings from the top of some prominent perch, with head raised and tail hanging downward. But its song is really its own and quite unique.
Laurence B. Potter writes to me: “The song of the sage thrasher is of the highest quality and, like that of the European skylark, is uttered without break or periods, as the brown thrasher. I have timed the song with my watch and have known it to continue 2½ minutes at a stretch. The sage thrasher also sings in flight in the manner of the western meadowlark.”
Dr. Wetmore (1920) describes the song very well as follows: “At its beginning the song is somewhat like that of a grosbeak. As the notes wander on, to change and become more intricate, burring calls, that while harsh are not unmusical, creep in as an accompaniment to clearer whistled notes that are varied and pleasing. Low trills and changing combinations mark the song, reminding one of the improvisation of some gifted musician who, playing apparently at random, brings forth tones that follow one another in perfect harmony.”
Ralph Hoffmann (1927) says: “Its song, given from the top of the sage or from a fence post along the road, is a long succession of warbling phrases with very little range of pitch and with constant repetition of one accented note. The bird’s alarm note is a chuck, chuck suggesting a blackbird, and a sweet high wheurr.”
Field marks: Though there is a fancied, superficial resemblance to the mockingbird in behavior, the illusion is soon dispelled when the bird takes to the air, for the conspicuous white areas in the wings of the mocker are lacking in the thrasher. The sage thrasher can be recognized as a plain brownish gray bird above, with a darker tail tipped with white on the outer feathers, with a short, straight bill, and with a breast distinctly streaked with black. None of the other thrashers need be confused with it.
Fall: The sage thrasher is a decidedly migratory species, retiring in fall from nearly all its breeding range and spending the winter near or beyond the southern boundary of the United States. Its migration is well marked and its numbers are sometimes impressive. Harry S. Swarth (1924) gives a good illustration of this, as observed in Arizona. The birds were “first seen September 11; a few days later this became the most abundant bird species in the piñon-juniper belt. The Sage Thrashers were obviously migrating, and some days all the birds seen would be rapidly moving southward, an advancing army really impressive in numbers. Scores were in sight at once on the ground, running from bush to bush, others were taking short flights through the trees, and still others were in scattered companies overhead, almost like flocks of bluebirds in flight. The usual call-note is a harsh chuck, suggestive of that of a blackbird, but some thrashers were heard giving fragments of their striking song from perches in the junipers.
“By the middle of October the number of Sage Thrashers had markedly diminished. On the 20th none were seen, but on the 28d two appeared, the last observed.”
Range: Central southern British Columbia to northern Mexico. Breeding range: The sage thrasher breeds north to central southern British Columbia (Keremeos, Similkameen Valley, and the Okanagan Valley as far north as Okanagan Landing); central Idaho (Junction); southern Montana (Hillside, Fort Custer, and Miles City); and southwestern Saskatchewan (Eastend). East to southeastern Saskatchewan (Eastend); eastern Montana (Miles City and Tongue River); eastern Wyoming (Midwest, Douglas, and Laramie); northwestern Nebraska, possibly (Sioux County); Colorado east to the Plains (Loveland, Golden, and Fort Garland); and extreme western Oklahoma (the Black Mesa region of Cimarron County). South to western Oklahoma (Cimarron County); northern New Mexico (Santa Fe, Albuquerque, and Mount Taylor); northern Arizona (Navajo, Apache County, and Fredonia); southern Nevada (Charleston Mountains); and southern California (San Bernardino and Lockwood Valley). West to California, southern and eastern parts of the State (Lockwood Valley, Bakersfield, Inyo Mountains, Mono Lake, Eagle Lake, and McDoel, Siskiyou County); Oregon, east of the Cascades (Spring Lake, Fort Klamath, and John Day River Valley); central Washington (Kiona, Yakima, and Ellensburg); and southern British Columbia (Keremeos).
Winter range: In winter the sage thrasher is found north to southern California (San Fernando, Twenty-nine Palms, sometimes to Coalinga, Fresno County, and Death Valley); southern Arizona (Sascaton and Tucson); southern New Mexico (Silver City and Mesilla); and southern Texas (El Paso, Fort Clark, and Kerrville). East to Texas (Kerrville, TJvalde, Laredo, and rarely Brownsville); and northern Tamaulipas (Nuevo Laredo and Camargo). South to Tamaulipas (Camargo); northern Chihuahua (Colonia Diaz and Chihuahua); northern Sonora (El Doctor, Sonoyta, and Punta Penascosa); and Baja California (Cape San Lucas). West to Baja California (Cape San Lucas, the Pacific coast, and occasionally Guadalupe Island), and California (San Diego and San Fernando).
Migration: L ate dates of spring departure are: Chihuahua: Palomas Lakes, April 7. Texas: Somerset, April 12. Arizona: Tucson, April 7.
Some early dates of spring arrival are: Texas: Somerset, February 10. New Mexico: Silver City, March 22. Arizona: Williams, March 31. Colorado: Walden, March 10. Utah: St. George, April 13. Wyoming: Laramie, March 27. Idaho: Rupert, March 31. Montana: Billings, May 1. Oregon: Klamath Lake, April 6. Washington: Yakima, April 10. Saskatchewan: Eastend, May 2.
Some late dates of fall departure are: Saskatchewan: Eastend, August 18. Washington: Yakima, September 15. Idaho-Meridian, September 21. Wyoming: Douglas, October 3. Colorado-Fort Morgan, October 4. New Mexico-Zuni, November 26.
Some early dates of fall arrival are: Arizona: Fort Verde, August 29. New Mexico-Carlsbad, August 6. Chihuahua: Chihuahua, October 5.
Casual records: On June 4, 1940, at Gleeson, Cochise County, Ariz., a bird still in juvenile plumage was collected; this is more than 250 miles south of the southernmost known breeding record for the State. A sage thrasher was recorded at Portland, Oreg., on August 12, 1924. There are two sight records for North Dakota: one at Medora on June 16, 1918, and one on April 24, 1930, in Woodbury Township, Stutsman County. A specimen was collected July 29, 1913, in Buffalo Valley, southwest Stanley County, S. Dak. One specimen was collected and four other birds seen on January 2, 1926, in Cameron Parish, La., only about 100 yards from the coast. On April 12, 1942, a specimen was collected near Braddock Bay, Monroe County, N.Y.
Egg dates: California: 24 records, April 19 to July 18; 12 records, April 19 to May 19; 9 records, June 4 to 25.
Utah: 44 records, April 30 to June 11; 22 records, May 13 to 31, indicating the height of the season.
Washington: 22 records, April 14 to May 20; 11 records, April 24 to May 9.