The loud, double whistle of the Curve-billed Thrasher is a distinctive and frequently heard sound throughout this species' range in arid lands of the southwestern United States and northern and central Mexico. Breeding males frequently call or sing from conspicuous perches; their song has no set pattern of specific notes and has been described as a "pleasing warble" or "abrupt phrasing." The double whistle, not given by other thrashers, appears to be an all-purpose note, used by both sexes for territorial defense, contact with mate or young, and alarm. Northern Mockingbirds (Mimus polyglottos) and European Starlings (Sturnus vulgaris) sometimes mimic the whistled call notes.
This heavy-legged ground forager pokes and probes in plant litter and digs holes in the soil with its long, decurved bill, searching for insects or seeds. It also eats berries from bushes and fruit from cacti when these are available. Its nest is a deep cup of twigs, lined with grasses or other fine materials, placed in a cholla cactus (Opuntia) or spiny shrub.
Of the southwestern species of Toxostoma, the Curve-billed Thrasher occurs in the broadest range of habitats and appears to have been least affected by the activities of people. At present, however, both of its preferred U.S. habitats - south Texas brushland and the Sonoran Desert in Arizona -are being transformed by development.
Two visually distinguishable groups of subspecies exist: the T. c. palmeri group in the Sonoran Desert of Arizona and northwestern Mexico and the T. c. curvirostre group in the Chihuahuan Desert and central Mexican plateau. Although these two forms with nearly allopatric ranges may be distinct species, their life histories are very similar.
Common names in this genus are confusing because several other thrashers have bills with more curvature than the Curve-billed Thrasher, but the other species were not known when W. Swainson published the first description of this species in 1827 from a specimen taken on the Mexican plateau.