Oreoscoptes montanus

Placed in Sturnidae in Sibley and Ahlquist (1984).

Large range in western North America; large population size; still widespread and numerous but declining in most of range; required sagebrush habitat is being lost, degraded, and fragmented as a result of ongoing conversion for human uses, effects of non-native plants, and climate change.

Breeding range extends from southern British Columbia, central Idaho, and south-central Montana southward through the Great Basin to eastern California, northeastern Arizona, and west-central and northern New Mexico (AOU 1983, Reynolds et al. 1999). Sage thrashers breed at least irregularly in southern Alberta and southern Saskatchewan (Cannings 1992). Nonnreeding range extends from central California, southern Nevada, central Arizona, central New Mexico, and central Texas south to southern Baja California, northern Sonora, Chihuahua, Durango, Guanajuato, northern Nuevo Leon, and northern Tamaulipas (AOU 1983, Reynolds et al. 1999).

The number of distinct occurrences has not been determined using standardized criteria, but this species is represented by a large number of recent observation sites (e.g., see eBird data) and locations (as defined by IUCN).

HABITAT LOSS, DEGRADATION, FRAGMENTATION: Large scale reduction and fragmentation of sagebrush habitats is occurring in many areas due to land conversion to tilled agriculture, urban and suburban development, and road and power-line rights of way. Range improvement programs remove sagebrush by burning, herbicide application, and mechanical treatment, replacing sagebrush with annual grassland to promote forage for livestock. Burning can result in longer-lasting sagebrush control than chaining (Castrale 1982). Range management practices such as mowing, burning, herbicide treatments, and residential and agricultural development have reduced the quantity and quality of sagebrush habitat (Braun et al. 1976, Cannings 1992, Reynolds 1999). In Wyoming, an increase in energy development (well density) did not result in a decline in sage thrasher populations, though possibly a decline might occur over a longer time frame (Gilbert and Chalfoun 2011).

GRAZING: Grazing can increase sagebrush density, positively affecting thrasher abundance. Dense stands of sagebrush, however, are considered degraded range for livestock and may be treated to reduce or remove sagebrush. Grazing may also encourage the invasion of non-native grasses, which escalates the fire cycle and converts shrublands to annual grasslands. West (1988, 1996) estimated that less than 1% of sagebrush steppe habitats remained untouched by livestock; 20% is lightly grazed, 30% moderately grazed with native understory remaining, and 30% heavily grazed with understory replaced by invasive annuals. The effects of grazing in sagebrush habitats are complex, and depend on intensity, season, duration and extent of alteration to native vegetation.

INVASIVE GRASSES: Cheatgrass readily invades disturbed sites and has come to dominate the grass-forb community of more than half the sagebrush region in the West, replacing native bunchgrasses (Rich 1996). Cheatgrass can create a more continuous grass understory than native bunchgrasses. Dense cheatgrass cover can possibly affect foraging ability for ground foragers, and more readily carries fire than native bunchgrasses. Crested wheatgrass and other non-native annuals have also altered the grass-forb community in many areas of sagebrush shrub-steppe.

FIRE: Cheatgrass has altered the natural fire regime on millions of acres in the western range, increasing the frequency, intensity, and size of range fires. Fire kills sagebrush and where non-native grasses dominate, the landscape can be converted to annual grassland as the fire cycle escalates (Paige and Ritter 1998).

Breeding range is projected to decrease by 78 percent between 2010 and 2099 as a result of ongoing climate change (van Riper et al. 2014).