Brown Thrasher Life History

Habitat

Habitat ScrubIn eastern North America, Brown Thrashers nest in thickets, hedgerows, forest edges, and overgrown clearings in deciduous forest. Farther west, in the Great Plains, they breed in fencerows, shelterbelts, and woody draws. They’re often found in woodlands with cottonwood, willow, dogwood, American plum, saltcedar, hawthorn, pitch pine, or scrub oak. On rare occasions they breed in backyards and gardens. Brown Thrashers winter in the southern part of their breeding range and also move into nonbreeding habitat throughout central Texas. They are the only thrasher east of the Rocky Mountains and central Texas.Back to top

Food

Food OmnivoreBrown Thrashers eat mostly insects and other arthropods along with some fruits, seeds, and nuts. They typically feed on the ground, sweeping their bills through the leaf litter and soil with quick, sideways motions. They also forage in clusters of dead leaves on trees, eat fruit right off of berry bushes, glean seeds from weed stems, and sometimes catch insects in the air. The animal portion of their diet includes many kinds of beetles, along with grubs, wire-worms, army worms, cutworms, tent caterpillars, gypsy-moth caterpillars, leafhoppers, treehoppers, cicadas, grasshoppers, crickets, wasps, bees, harvestmen, sowbugs, lizards, snakes, and tree frogs. The fruit portion of their diet includes blueberry, huckleberry, holly, elderberries, pokeberries, hackberries, Virginia creeper, sour gum, bayberry, sumac, raspberry, currant, grape, cherry, and strawberry.Back to top

Nesting

Nest Placement

Nest ShrubThe male and female both help select the nest site, usually low in a tree or thorny shrub. They use forsythia, privet, gooseberry, sumac, Osage-orange, multiflora rose, eastern redcedar, elm, and honey locust. Occasionally they nest right on the ground.

Nest Description

Males and females collaborate on the nest, a bulky cup made of twigs, dead leaves, thin bark, grass stems, and well-cleaned rootlets. The inside of the cup is a couple of inches deep and 3.5 inches across. If they start early in the season, the pair will spend up to a week building a nest, whereas later in the season they may complete one in just a few days.

Nesting Facts
Clutch Size:2-6 eggs
Number of Broods:1-2 broods
Egg Length:1.0-1.1 in (2.6-2.7 cm)
Egg Width:0.8-0.8 in (1.9-2 cm)
Incubation Period:10-14 days
Nestling Period:9-13 days
Egg Description:Glossy pale blue, pale greenish blue, or white, with many red-brown speckles.
Condition at Hatching:Eyes closed; pink skin with scattered tufts of gray-white down.
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Behavior

Behavior Ground ForagerBrown Thrashers spend most of their time near or on the ground, walking, running, or hopping. When disturbed at the nest, they drop to the ground and dart into dense cover. They feed by sweeping their long bills through leaf litter to uncover insects and other invertebrates. They are slow, short-distance fliers with a distinctive jerky, fluttering flight style. Brown Thrashers are monogamous during a breeding season, but it isn’t known whether pairs stay together from year to year. They breed in such dense vegetation that little is known of their courtship; the few observations that exist suggest that a courting pair presents each other with twigs or dead leaves, after which the male may briefly chase the female before mating. They defend territories of variable size, and they are very aggressive toward intruding Brown Thrashers and toward potential nest predators, which include snakes (racers as well as garter, king, rat, bull, and milk snakes) and dogs. Sometimes Brown Thrashers strike predators with their bills hard enough to draw blood.Back to top

Conservation

Conservation Low ConcernBrown Thrashers are fairly common birds but their numbers have been declining for the last several decades. According to the North American Breeding Bird Survey, between 1966 and 2015 populations declined by 41%. Partners in Flight estimates the global breeding population at 4.9 million, with 100% spending some part of the year in the U.S., and 8% breeding in Canada. They rate an 11 out of 20 on the Continental Concern Score and are not on the 2016 State of North America's Birds' Watch List, although they are a U.S.-Canada Stewardship species. Brown Thrashers probably increased their range during the nineteenth and twentieth centuries, as humans cleared forests for agriculture, suppressed fires in the Great Plains, and put out bird feeders. However, their shrubby habitat is now declining throughout the eastern U.S. as fields and forests regrow or are cleared altogether. Competition with Northern Mockingbirds may be affecting their numbers in northern parts of their range. Brown Thrashers often die in collisions with television towers (during migration) or with cars (since they often occur in roadside habitat). They can become unintended casualties of pesticides that people use to control insects, including organophosphates used in pecan plantations, dieldrin used on fields, and heptachlor used to combat Japanese beetles.Back to top

Backyard Tips

Brown Thrashers may come to backyards if food is offered. Sometimes they visit feeders or the ground below to pick up fallen seed. There is a better chance they will visit if dense cover is close by. You can also attract them by planting shrubs that produce berries. Find out more about what this bird likes to eat and what feeder is best by using the Project FeederWatch Common Feeder Birds bird list.

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Credits

Cavitt, John F. and Carola A. Haas. 2014. Brown Thrasher (Toxostoma rufum), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski, Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.

Sibley, D. A. (2014). The Sibley guide to birds, second edition. Alfred A. Knopf, New York, USA.

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