The brown thrasher is a medium-sized songbird found throughout much of the eastern and central United States. It prefers open woodland habitats with thick, low vegetation and is often found in forest edges, overgrown fields, hedgerows, and suburban gardens and yards. The brown thrasher has a loud, repetitive song and an aggressive nature, defending its territory aggressively against intruders. Its brown upperparts and heavily streaked underparts provide good camouflage in brushy habitats.
Geographic Range
The brown thrasher has a large geographic range across much of the eastern and central United States. Its breeding range extends from southern Ontario and Quebec west to eastern Montana, Wyoming, and eastern Colorado and south to central Texas, the Gulf Coast, southern Georgia and Florida. The northern limits of its breeding range include southern Michigan, southern Wisconsin, southern Minnesota, and south-central South Dakota.
In the western half of its range, the brown thrasher’s northern limit dips further south, avoiding higher elevations and drier climates. It is largely absent from the Appalachian Mountains but can be found in valleys and on western slopes.
The brown thrasher winters primarily in the southern United States. It withdraws completely from the northern portions of its breeding range. Most winter from Texas east to North Carolina and south throughout Florida and the Gulf Coast. It is mostly absent in winter from the lower Mississippi Valley.
Breeding Range
During the breeding season, the core of the brown thrasher’s range centers on the east-central United States, including Missouri, Arkansas, Louisiana, Mississippi, Alabama, Tennessee, Kentucky, Illinois, Indiana, and Ohio. Farther north, it breeds locally up to the Canada border. In the northeast, it breeds inland, avoiding higher elevations and the immediate Atlantic Coast.
Westward, it breeds widely but patchily, absent from high plains and mountains but occurring locally in river valleys and canyons. Breeding reaches west to eastern Montana, Wyoming, Colorado, and central Texas. Isolated breeding populations occur in riparian woodlands in western Nebraska, western Kansas, eastern New Mexico, and central Texas.
Along the Atlantic Coast, breeding distribution is centered on the Piedmont and Coastal Plain from southern Maryland south to Georgia and inland portions of Florida. Breeding becomes localized and sparse southward through peninsular Florida.
Wintering Range
The brown thrasher withdraws completely from the northernmost parts of its breeding range in winter. In the northeast, most winter from New Jersey, Maryland, and Virginia southward, although some may linger as far north as southeastern Pennsylvania and Long Island. Along the Atlantic Coast, most winter from North Carolina southward, with smaller numbers reaching South Carolina and only scattered individuals in Georgia and Florida.
In the southeast, winter distribution centers on western Florida north to Georgia and west to the Gulf Coast, southern Arkansas, Louisiana, eastern Texas, and southeastern Oklahoma. Numbers decrease northward into eastern Texas and Oklahoma.
Farther west, most winter from eastern Texas and Oklahoma south into northeastern Mexico, avoiding higher elevations. Scattered wintering occurs north to southern Kansas. Along the West Coast, small numbers reach southern California and may winter sporadically.
Habitat
The brown thrasher inhabits a variety of open, brushy habitats across its range, typically those with dense low vegetation that provides cover. Common habitats include:
Thickets and Hedge Rows
Brown thrashers favor tangled thickets with dense shrubs, small trees, and vines. They often inhabit overgrown fencerows and hedgerows dividing fields or surrounding meadows. The density of vegetation provides cover while allowing movement low to the ground. Typical shrub species used include dogwood, blackberry, wild grape, buckthorn, honeysuckle, and others.
Forest Edge and Open Woodlands
Forest edges, second growth forests, lightly grazed woodlots, overgrown clearcuts, and open pine-oak woodlands interspersed with thickets provide prime habitat. The brown thrasher uses the dense low growth for nesting and cover while also foraging on the forest floor.
Shrubby Areas and Thickets in Suburbs and Parks
As human settlement has expanded, the brown thrasher has adapted to using suitable shrubby habitat in suburban yards, parks, cemeteries, golf courses, shelterbelts, and other open areas with shrubs and small trees. Nesting often occurs close to human habitation where thickets abut houses or other buildings.
Scrublands and Brushy Desert Wash
In the southwestern U.S., brown thrashers occur in desert scrub habitats, especially washes and drainages with dense brush. They also inhabit mesquite and acacia scrublands where brush is thick enough to provide nesting cover.
Regenerated Clearcuts and Burns
Logged or burned-over areas that have regrown with a dense stand of shrubs, young trees and vines provide temporary habitat. As vegetation matures, density and cover decrease and brown thrashers will abandon the area.
Nesting
The brown thrasher builds a well-concealed nest low in dense shrubs or small trees. Nest sites typically provide dense cover overhead and around the nest:
Shrubs and Small Trees
In shrublands, typical nest sites include dogwood, blackberry, raspberry, honeysuckle, rose, buckthorn, and other dense, low shrubs. In open woodlands, nests are often built in small trees such as dogwood, hawthorn, elm, oak, or eastern red cedar. Nests average 3-5 feet above ground.
Vines and Briars
Vines and briars that form dense ground cover are also used for nesting. Common sites include wild grape, greenbriar, blackberry, and exotic species like Japanese honeysuckle and multiflora rose. The nest may be completely hidden in the vines.
Nests of Other Species
Brown thrashers sometimes build their nest on top of an existing nest of another species, such as a robin’s nest. The old nest provides a foundation while the thrasher adds material to create a new nest.
Manmade Sites
Where natural sites are limited, brown thrashers may nest in multiflora rose or honeysuckle growing on chain link fences, in backyard shrubs against houses, or in exotic shrubs in urban parks and cemeteries.
Nest Description
The nest is a bulky cup built of twigs, grass, bark strips, leaves, trash, and other available material. It is lined with finer material such as fine grass, hair, or rootlets. Nests are typically 4-5 inches tall and 5-6 inches across outside, with a cup 2-3 inches deep and 3-4 inches across.
Feeding
The brown thrasher is an omnivore that feeds on both plant and animal material. It mainly forages on the ground, using its long bill to probe into soil and leaf litter. Common foods include:
Invertebrates
A major portion of the diet consists of invertebrates, especially during the breeding season when protein needs are high. Common prey includes beetles, crickets, grasshoppers, caterpillars, spiders, millipedes, snails, and worms. Brown thrashers hunt by probing soil and litter and overturning leaves to uncover prey.
Fruit and Berries
Fruits and berries become important in the diet, especially in late summer, fall, and winter. Favored foods include wild grapes, blackberries, raspberries, dogwood and pokeweed berries, mulberries, and hackberries. Brown thrashers pluck fruit from shrubs or glean dropped fruit from the ground.
Seeds and Grains
A variety of seeds and grains are consumed, especially weed seeds, grass seeds, acorns, pine seeds, and grain such as corn, wheat, sorghum, and oats. Brown thrashers forage seeds from the ground or knock them loose from plants.
Other Foods
Other food items include buds, catkins, tubers, fungi, nectar, flowers, nuts, and occasionally small vertebrates such as lizards, frogs, mice, and the eggs and young of other birds. Brown thrashers adopt a varied diet depending on locally and seasonally available foods.
Threats and Conservation
Overall, the brown thrasher has a large, stable population estimated at 13 million birds. However, populations have declined in some regions, primarily due to habitat loss. Major threats and conservation priorities include:
Habitat Loss
Conversion of scrubby, open habitats to agriculture and development has caused habitat loss and population declines, especially in northeastern states. Preservation of remaining key habitats is a priority.
Nest Parasitism
Brown thrashers are vulnerable to brood parasitism by brown-headed cowbirds, which lay eggs in thrasher nests. Controlling cowbird populations may aid thrashers where nest parasitism is a factor in declines.
Pesticides
Brown thrashers are exposed to pesticides used in agriculture and landscapes. Some studies indicate pesticide exposure may impact physiology and reproduction. Maintaining habitats with natural food sources may help offset effects.
Climate Change
Modeling suggests the core of the breeding range may shift northward under climate change scenarios, reducing southern populations. Preserving northward habitat connections could facilitate range shifts.
Predation
Natural predators of eggs and young include snakes, crows, jays, raccoons, cats, and other species. Predation pressure has likely increased near human habitation. Public education can encourage cat owners to keep cats indoors.
Population and Distribution Trends
Breeding Bird Survey data indicates the brown thrasher population trended downward in the eastern U.S. from 1966-2015 while generally increasing in the Great Plains and western states:
Eastern Breeding Bird Survey Region
Time Period | Trend (% change per year) |
1966-2015 | -1.44 |
2005-2015 | -0.91 |
Great Plains Breeding Bird Survey Region
Time Period | Trend (% change per year) |
1966-2015 | +0.11 |
2005-2015 | +1.03 |
Western Breeding Bird Survey Region
Time Period | Trend (% change per year) |
1966-2015 | +0.41 |
2005-2015 | +1.29 |
Range-wide
Range-wide Breeding Bird Survey data shows an overall stable population trend from 1966-2015. Regional declines in the east have been offset by increases in the Great Plains and west.
Conclusion
The brown thrasher is a widespread songbird of the central and eastern United States, favoring brushy, open habitats with dense low vegetation. Its populations have declined in Northeastern and some Southeastern states due to habitat loss but remain stable or increasing through much of its range. Preserving remaining scrubby habitat in the east and maintaining habitat connectivity to allow northward range shifts under climate change are conservation priorities. While still common through most of its range, more habitat-specific than related species, the brown thrasher warrants continued monitoring and habitat protection to maintain populations.