This thrasher, the only one east of the Rocky Mountains and central Texas, inhabits thickets and hedgerows in deciduous forest clearings and forest edge in the eastern United States. Farther west, within the Great Plains, it commonly breeds in fencerows, shelterbelts, and woody draws. Because of its tendency to forage on the ground and skulk in dense brush when disturbed, it is less often seen than heard. Although not as well recognized for its vocal abilities as the Northern Mockingbird (Mimus polyglottos), it is a remarkable singer with one of the largest repertoires of any North American passerine.
Brown Thrashers have long, heavy legs, characteristic of a ground foraging bird, and spend considerable time sweeping the litter and soil layer for insects, fallen seeds, and berries. The long, slightly curved bill of this species is generally used to uncover prey items with rapid side-to-side motions. During the breeding season (May–June), individuals feed chiefly on insects and other arthropods, but by late summer rely more heavily on fruit and berries.
Pairs usually nest low in a tree or shrub, occasionally on the ground. Both sexes incubate the clutch of 3–5 eggs and feed young, which fledge relatively quickly for a passerine of this size, sometimes leaving the nest fully feathered in 9 days—an adaptation that may help reduce high rates of nest predation commonly seen in shrub-nesting species. Brown Thrashers are the largest common host of Brown-headed Cowbirds (Molothrus ater), although they often reject the eggs of this parasite.
Systematic relationships to other thrashers are discussed in Engels 1940 , Mayr and Short 1970 , Klicka and Zink 1997 , and Zink et al. 1999 . Information on many aspects of breeding biology are available from studies in Kentucky ( Partin 1977 ), Tennessee ( Erwin 1935 ), Iowa ( Gabrielson 1912 ), North Dakota (Haas Haas 1985 , Haas 1990 , Haas 1995 , Haas 1997 ; Haas and Haas 1998 ), and Kansas (Cavitt Cavitt 1998 , Cavitt 1999 ; Cavitt et al. 1999 ). Winter ecology is known from a single study in Texas (Fischer Fischer 1981a , Fischer 1981b ).
Even though this species is widespread in eastern North America, much remains to be learned about its behavior and ecology, particularly during the nonbreeding season. Future studies of migration routes, control and physiology of migration and orientation, foraging ecology, and reproductive biology (particularly geographic variation, fledgling behavior, and development) will be valuable.