Sage Thrasher Life History

Habitat

Habitat ScrubThe Sage Thrasher breeds exclusively in shrubsteppe habitats—the vast, open landscapes of the interior West. These areas tend to be so dry that trees don’t grow, and the ground is dominated by big sagebrush (Artemisia tridentata) and other sagebrush species. Sage Thrashers require relatively dense ground cover for concealment, but also some bare ground for foraging and for getting around on their feet, which they often do in preference to flying. Thrashers tend to be more numerous in areas dominated by sagebrush, a small amount of grasses, and some bare ground. During migration and wintering, Sage Thrashers use arid or semiarid open country with scattered bushes, grasslands, and open pinyon-juniper woodlands.Back to top

Food

Food InsectsSage Thrashers feed primarily on terrestrial insects and arthropods, such as ants, grasshoppers and ground beetles, which they often capture while running on the ground amid sage cover. They also forage on berries and grapes, and have been seen digging for crickets. They forage alone during the breeding season, and occasionally in small groups after breeding. Back to top

Nesting

Nest Placement

Nest ShrubNests are built on or near the ground, most frequently in the tallest big sagebrush (Artemisia tridentata) around, particularly ones with wider crowns. Sage Thrashers usually place their nests under the densest part of the shrub, possibly to provide shading from the heat, or cover from aerial predators. Some nests are even built underneath the previous year’s nest, taking further advantage of overhead cover.

Nest Description

Both sexes help build the nest. The bulky twig nests are lined with grasses, rootlets, or hair and fur. Externally, nests measure about 4 inches tall and up to 8 inches across. The cup averages 1.8 inches deep for first nests and 3.2 inches for second nests.

Nesting Facts
Clutch Size:4-5 eggs
Number of Broods:1-2 broods
Egg Length:0.9-1.0 in (2.28-2.61 cm)
Egg Width:0.7-0.8 in (1.68-1.9 cm)
Incubation Period:11-17 days
Nestling Period:8-14 days
Egg Description:Eggs are a vibrant turquoise with heavy splotches of chestnut brown.
Condition at Hatching:Nestlings have translucent reddish-orange skin, turning grayish yellow with time, and are covered with tracts of blackish down within a few days.
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Behavior

Behavior Ground ForagerSage Thrashers become especially shy during breeding, and prefer running secretively, tail cocked upward, rather than taking flight. However, during territory establishment, male Sage Thrashers sing while performing circular, undulating flights through the sagebrush, often sweeping low amid the vegetation. Upon alighting, and during song, they raise and flutter both wings in a display called the bilateral wing display. As with most songbird species, their songs help them both attract mates and to define territory boundaries. Males often sing back and forth with a neighbor on the border between their two territories. Adults are extremely secretive around their nests, and when returning to the nest will typically fly to within about 30 feet of the nest and then sneak the rest of the way on foot. Both sexes share equally in incubating eggs, and feeding and brooding the young. Both parents also remove eggshells and fecal sacs from the nest. During migration and the nonbreeding season, Sage Thrashers can form impressive flocks numbering in the hundreds, suggesting some level of sociality away from breeding territories.Back to top

Conservation

Conservation Low ConcernSage Thrashers are numerous but their populations declined by almost 1.5% per year between 1966 and 2014, resulting in a cumulative decline of 52%, according to the North American Breeding Bird Survey. Partners in Flight estimates a global breeding population of 5.9 million, with 100% spending some part of the year in the U.S., and 48% wintering in Mexico. A small part of the population may breed in Canada. The species rates an 11 out of 20 on the Continental Concern Score. Sage Trasher is a U.S.-Canada Stewardship species and is not on the 2014 State of the Birds Watch List. Compared to most sagebrush-dependent birds, Sage Thrasher populations so far are faring well in the face of development. Nevertheless all birds that depend on sagebrush landscapes are vulnerable to habitat loss and fragmentation due to heavy lifestock grazing, residential development, agricultural conversion, herbicide and pesticide treatments, and changes to fire regimes. These combined changes have led to a loss of 50 percent of the sagebrush steppe habitat in Washington, and the species is nearly extirpated from Canada altogether. The loss of sagebrush habitat to invasive cheatgrass and crested wheatgrass are also threats rangewide.Back to top

Credits

North American Bird Conservation Initiative. 2014. The State of the Birds 2014 Report. US Department of Interior, Washington, DC, USA.

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

Reynolds, Timothy D., Terrell D. Rich and Daniel A. Stephens. 1999. Sage Thrasher (Oreoscoptes montanus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

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

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