Merlin

Curve-billed Thrasher Life History

Habitat

Habitat Scrub

Curve-billed Thrashers in the eastern part of the range (curvirostre group) dwell in open country of many kinds, including brushlands, thorn scrub with mesquite, thickets bordering woodlands, pinyon-oak woods, and desert flats with prickly pear, yucca, and cholla cactus. To the west, the Sonoran Desert population (palmeri group) favors similar habitats that usually hold creosote bush, saguaro, palo verde, and cholla. Farther north, in the plains of Colorado, grasslands with cholla provide habitat.

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Food

Food Insects

Curve-billed Thrashers eat a variety of insects, spiders, and snails, along with fruit and seeds. They forage on the ground, using the bill to sweep back and forth through leaf litter and soil. They toss large pieces of vegetation—even “flipping cow chips”—to one side to uncover insect prey. Curve-billed Thrashers do not use their strong legs for scratching in leaves, as some thrashers do; rather, the legs provide leverage, and the tail is also used as a support. They pluck ripe berries from perches in trees or bushes and sometimes eat flowers, such as of the agave plant. They also eat seeds of saguaro and other cactus, and it is likely that cactus fruit supplies much-needed water during the warm spring and early summer, before the late-summer rains arrive.

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Nesting

Nest Placement

Nest Shrub

Most nests are constructed 3–5 feet above ground in shrubs, small oaks, acacia, mesquite, cholla, prickly pear, nopalo, mistletoe, and yucca, though some as low as 1 foot and as high as 9 feet have been reported. A few nests have even been discovered inside cavities in large saguaro and sycamore trees.

Nest Description

Both male and female build the bulky nest. Twigs form the foundation of the nest, which is then lined with grass by the female, who shapes the cup with her body. Just she lays her eggs, the female adds flowers or other fresh plants. Sometimes, pairs build multiple nests before selecting one for egg-laying, and they frequently build less elaborate nests for roosting during the nonbreeding season. Nests measure about 9 inches in diameter and 7 inches tall, with the interior cup 4.2 inches in diameter and 3.9 inches deep.

Nesting Facts
Clutch Size:3-5 eggs
Number of Broods:1-2 broods
Egg Length:1.0-1.3 in (2.6-3.3 cm)
Egg Width:0.7-0.9 in (1.8-2.2 cm)
Incubation Period:12-15 days
Nestling Period:11-16 days
Egg Description:

Light bluish-green to pale yellow with reddish-brown speckling

Condition at Hatching:

Nearly naked and helpless with sparse long gray down.

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Behavior

Behavior Ground Forager

Curve-billed Thrashers are animated birds, their gait often hurried and jerky as they run or hop through their thorny habitat. Pairs mate for life and maintain their territory year-round, usually about 5–11 acres. Perhaps because of this strong pair bond, courtship displays are rare—apparently involving chases, chase-flights, and quiet countersinging as the birds face each other. More apparent are territorial clashes between males, which often involve aerial battles in which combatants lock bills and fall to the ground, flapping and kicking. Curve-billed Thrashers are especially irascible if others of its species approach their nest too closely, but they nest in harmony next to Bendire’s, Long-billed, and Crissal Thrashers. Other species, such as Cactus Wrens or Bronzed Cowbirds, are frequent targets of attacks by male Curve-billed Thrashers, which also destroy the roost-nests of Cactus Wrens in their territory. Forages on ground, pokes and probes in plant litter, and digs holes in the soil with its long, down-curved bill.

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Conservation

Conservation Low Concern

Curve-billed Thrasher are fairly common, but their populations declined by just under 1% between 1966 and 2015 (representing a cumulative decline of about 14% over the whole period), according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 3.4 million. The species rates a 9 out of 20 on the Continental Concern Score, indicating it is a species of low conservation concern. Long-term declines may be due to the loss of habitat to urban development and agriculture in south Texas brushlands and Arizona’s Sonoran Desert.

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Backyard Tips

This species often comes to seeds, berries, insects, and water if offered, particularly on platform feeders or on the ground. Curve-billed Thrashers can sometimes dominate smaller birds at feeding stations. Large yards might even host a nesting pair in native vegetation. Find out more about their food and feeding station preferences at the Project FeederWatch Common Feeder Birds bird list.

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Credits

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.

Tweit, Robert C. (1996). Curve-billed Thrasher (Toxostoma curvirostre), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

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