The Long-billed Thrasher is a resident of southern Texas and eastern Mexico, where it maintains territories in dense brushy habitats. In common with other members of its genus, it forages on the ground for insects and other small animals, ascending into shrubs and trees to eat berries in fall and winter. Its flights are generally limited to short distances near the ground. Males are most easily seen when they sing from conspicuous perches during the breeding season. Although these songs are important in territory defense, calls are the primary means of communication with mates and other birds.
The Long-billed Thrasher is one of several apparently closely related species of similar appearance with breeding ranges that rarely overlap. Its close relative the Brown Thrasher (Toxostoma rufum) breeds throughout much of eastern North America and migrates south to winter in the southeastern United States from Texas to Florida. The northernmost part of the Long-billed Thrasher's range overlaps the winter range of the Brown Thrasher. Another closely related member of this genus, the Ocellated Thrasher (T. ocellatum) is a permanent resident of the central plateau in Mexico at higher elevations than Long-billed Thrasher. The Cozumel Thrasher (T. guttatum), endemic to Cozumel Island off the coast of the Yucatán Peninsula, may also be a member of this complex.
The Long-billed Thrasher's life history has been considered very similar to that of the Brown Thrasher (except for migration) and consequently has been generally ignored. Most of our knowledge of this species' life history is due to the work in southern Texas of David H. Fischer (Fischer 1978a, Fischer 1979b, Fischer 1979c, Fischer 1980, Fischer 1981b, Fischer 1983).
In Texas, the Long-billed Thrasher is most common in dense brush in the lower Rio Grande River valley, but at least 95% of this habitat has been cleared. Additional breeding habitat has been created north of the valley by the invasion of grassland by mesquite and shrubs, but breeding densities appear lower in these areas. The population probably has been considerably reduced in Texas in the last 60 years. More data are needed on population and habitat changes in Mexico.