D e s e r t E x p o s u r e
June 2011
Southwest Wildlife
The Bird's Got Talent
The curve-billed thrasher may not look like much,
but it sure can sing.
by Jay Sharp
Like Susan Boyle — that ugly duckling of a woman who astonished the world with her glorious voice — the curve-billed thrasher, a drab-colored member of the bird world, delights the ear with its extemporaneous and melodic song.
 |
Curve-billed thrasher perched at the top of a honey mesquite. (All photos by Jay W. Sharp) |
As you may recall from a couple of years ago, Boyle, a dowdy middle-aged small-town Scottish woman who had never been kissed, let alone married, appeared before a cynical, smirky audience in the television show "Britain's Got Talent." She stunned and captivated spectators and judges plus millions of viewers with her performance of "I Dreamed a Dream" from Les Miserables. (Visit YouTube to see her performance again.)
Similarly, the curve-billed thrasher is a dull-colored ground forager that digs in the dirt with its dark, curved bill. But then it takes a perch, perhaps at the top of a honey mesquite or a cholla cactus, and produces captivating improvisational songs that famed naturalist Roger Tory Peterson described as "a musical series of notes and phrases." National Geographic characterized the curve-billed thrasher's song as "long and elaborate, consisting of low trills and warbles, seldom repeating phrases."
Distinctive Features
Typically, you will find the curve-billed thrasher (Toxostoma curvirostre) foraging, workmanlike, on the ground beneath shrubs and cacti. The bird uses its strong, downwardly curving ("decurved") bill and robust legs and feet to shuffle through plant litter and dig into the soil in its search for seeds and insects.
 |
Curve-billed thrasher perched on the trunk of a honey mesquite. |
Two quite similar subspecies occur in the Southwest. You are most likely to see the Toxostoma curvirostre curvirostre in southwestern New Mexico. You are more likely to see the Toxostoma curvirostre palmeri across southern Arizona. Both subspecies measure about the same length as a mockingbird, although they are somewhat heavier bodied. Both have predominantly brownish-gray plumage across the head, back, sides and tail, and they have buff- to cream-colored mottled plumage on the throat and breast. Both have yellowish-orange eyes and blackish bills, and they have the strong legs and feet typical of ground-foraging birds. In both species, the male and female look very much alike. The principal difference between the two species is that the T. c. curvirostre found in New Mexico has a lighter breast and throat with more contrasting mottling, and it has more distinct white wing bars and white-tipped tail feathers.
In his articles about the curve-billed thrasher in Cornell's The Birds of North America Online, authority Robert C. Tweit — my principal source for this article — says that the boundary between the two species is blurred. Much more research is needed, Tweit adds, if we are to understand the distribution in New Mexico.
Range
The curve-billed thrasher occupies a sprawling range. In the United States, the bird occurs most commonly in the southern halves of New Mexico and Arizona and the western two-thirds of Texas. A few year-round populations occur in western Oklahoma, southwestern Kansas and southeastern Colorado. In Mexico, the bird occurs from the northern states of Sonora and Chihuahua southward all the way to Oaxaca, south of Mexico City. It inhabits lower elevations from the Sea of Cortez eastward to the Gulf of Mexico.
Some populations in the northern parts of the bird's range — for instance, in southern New Mexico and southern Arizona — may migrate over limited distances, moving from mountain flanks down into desert basins during the winter and returning from the basins to the mountain flanks in the summer. Other populations appear to remain in the same area year round.