The Crissal Thrasher inhabits desert washes and riparian thickets in the Colorado River and Rio Grande valleys and their tributaries in southwestern North America; elsewhere to the south and southeast within its extensive range it may be found on brushy plains, in foothill scrub, or venturing into open piñon-oak-juniper (Pinus-Quercus-Juniperus) woodlands where there is a shrubby understory. Although widely distributed from southeastern California and southwestern Utah to central Mexico, the Crissal Thrasher remains poorly known, and the dearth of comprehensive data on the species seems attributable to two of the bird's notable characteristics: first, its preference over much of the U.S. range for dense, brushy habitats, which in desert landscapes are generally infrequent, patchily distributed, and often narrowly restricted to larger arroyos (dry washes) or mesquite (Prosopis spp.) thickets; and second, its decidedly reclusive habits. These attributes are a considerable handicap to studies requiring extended observation at close quarters.
In the early days of western American ornithology the Crissal Thrasher was widely confused with its close relative the California Thrasher (Toxostoma redivivum). In John Cassin's account (1856; re-published Cassin 1991) of 50 western North American birds, no fewer than 3 contributors to his California Thrasher treatment clearly refer to Crissal Thrasher rather than to its strictly Californian relative. Dr. T. C. Henry, an army surgeon stationed at several New Mexican forts (including Fts. Thorn and Fillmore), sent the first specimens of the Crissal Thrasher via John Cassin to Spencer Baird at the Smithsonian Institution in Washington, apparently believing he had secured a California Thrasher (Henry 1855). Baird's description of the new thrasher was later published under its collector's name (Henry 1858).
The Crissal Thrasher is a spectacular bird in many ways. In the stark and sparsely populated desert canyons and washes where it is most often found, it stands out as a singularly fine vocalist; typically thrasherlike, its song is sweeter and mellower than the harsher, more forceful song of the California Thrasher, and more deliberate and less hurried and blurry than the song of Le Conte's Thrasher (T. lecontei), its two closest relatives. When it is finally observed, the Crissal Thrasher is seen to have great style, dashing along the ground from one bush to the cover of another with tremendous verve. Although of medium size for a thrasher, the bird gives the impression of a larger presence as it spurts between patches of cover with outstretched head and long tail extended back. On closer observation, its plain appearance is offset by a long, sickle-shaped bill, occasional glimpses when the tail is raised of its strikingly reddish cinnamon crissum, and buoyant, energetic, and entertaining foraging behavior as it explores with active, probing bill and long, sturdy legs the potential arthropod prey beneath a dense shrub.
Although considered a permanent resident throughout much of its range, there is evidence for some local movements away from breeding habitats in the off-season, at least in northwestern parts of the range. The breeding season is protracted, extending at least from February to July, and in the winter rainfall part of the range, to the northwest, a new season is heralded by territorial singing with renewed vigor in the fall. Crissal Thrasher nests are placed most often in the interior of low, dense bushes, usually in the densest cover available in the habitat. Nests are solid but not excessively bulky, and can appear insubstantial when occupied by 3 nearly-fledged young. Unlike those of other thrashers (Toxostoma spp.), the eggs are unspotted and a striking robin's-egg blue. The amazingly elusive behavior of the parents around the nest is universally acknowledged; the parents reach their nest and leave the home bush on the ground with uncanny stealth and an impressive facility for keeping some form of cover between them and the observer (who they quite readily perceive) at all times.
The nomenclatural history of the Crissal Thrasher has been extremely contentious; it was reviewed in detail by Hubbard (Hubbard 1976). The original 1858 publication was plagued with several printer's errors, one of which transposed, to Spencer Baird's chagrin, the specific name of the new thrasher with that of a new junco (Junco dorsalis). The error was corrected (from T. dorsalis to T. crissalis) in a reprinted version the following month, and earlier references used this corrected form for more than 60 years. However, for a half century following Oberholser's (Oberholser 1920c) insistence on the legal precedence of T. dorsalis, this epithet identified the species in ornithological literature. In 1983, the International Commission on Zoological Nomenclature eventually endorsed a return to the originally intended name, and the Crissal Thrasher became permanently T. crissale .
As in the other thrashers of the genus, aspects of the morphology, ecology, and behavior of the Crissal Thrasher are shared by ecological counterparts in scrubby habitats elsewhere in the world. In size and coloration, tail length, and bill curvature, and in terrestrial foraging habits within scrubby vegetation, similarities to Crissal Thrasher are shown by babblers (Timaliidae: Pomatostomus) in Australia, by certain Old World larks (Alaudidae: Alaemon, Chersophilus, Chersomanes), by the Central American Queo (Thraupidae: Rhodinocichla rosea; Skutch 1962a), and especially by the bandurillas (Furnariidae: Upucerthia) in Chilean matorral (Cody 1974, Cody and Mooney 1978).
This account draws on several valuable early accounts of natural history and breeding biology (e.g., Mearns 1886a, Gilman Gilman 1902b, Gilman 1909a, Brandt 1951), as well as recent studies (Kozma et al. 1999, B. W. Anderson, R. D. Ohmart, and P. E. Russell unpubl.) in New Mexico and on the lower Colorado River. MLC's fieldwork on Crissal Thrashers was conducted in Arizona (e.g., Cody 1974) and more recently in the Mojave Desert of California (unpubl.). Beyond general information on distribution and habitat relations within its U.S. range, information on this species is sparse, and little is written on Mexican populations; in general, many questions on breeding biology, feeding ecology, survivorship, dispersal, nesting, and other behavior remain unanswered. Inevitable comparisons are drawn throughout this account to the closely related California Thrasher (see Cody 1998).