Montana Field Guide

Sage Thrasher - Oreoscoptes montanus

The Sage Trasher is unique in being the only thrasher in the genus Oreoscoptes. Genetic work indicates this species may be more closely related to the mockingbrds (Mimus) than to other thrashers (Toxostoma). Its long, melodious, mockingbird-like song, earned it the original name of Mountain Mockingbird. It is the smallest thrasher and is a sagebrush obligate species.

The bill and tail of this thrasher are relatively short compared to that of other thrashers. While the male is slightly larger than the female, they are similar in plumage characteristics. Adults are brownish-grey with some indistinct dark streaking on the back and crown. A dark streak through the eye separates the upper and lower lighter areas of the face. The malar region is also light with a darker line present along the sides of the throat. The bill is dark and short and the eyes are yellow to amber in color. Their underparts are generally off-white with bold dark marks. The Sage Thrasher is most easily recognized from other thrashers by its small size and short, relatively straight bill.

Montana Range




Range Comments
The distribution of this species is dependent upon the presence of appropriate sagebrush habitat. The majority of our population is found in the southwest, south-central, and south-eastern portions of the state.

This thrasher tends to stay in sagebrush plains and shrublands during migration. It will rarely visit areas of human habitation. Spring migration generally occurs from April 25 to May 15, with fall migration from July 30 to August 15.

The species is considered a sagebrush obligate in Montana (it is known to use black greasewood in Utah and Nevada and bitterbrush in Washington). Sage Thrasher abundance is generally positively correlated with the amount of sage cover and negatively correlated with grass cover.

Insects, other arthropods, and some plant materials make up the bulk of their breeding season diet, while small fruit (berries) may also be consumed if available. This species generally forages on the ground.

Nesting occurs soon after arrival to the breeding grounds. The nests may be placed on the ground, but are generally built in sagebrush. The bulky nests are cup-shaped and are constructed of twigs, forbs, and grass. Finer materials are used to line the nest. The 3 to 5 eggs are incubated by the females and males. Both sexes also tend the young. Montana's breeding dates are probably similar to those recorded for Wyoming: as early as May 17 and as late as mid-July.

Sage Thrashers need continuous stands of dense big sagebrush. Fragmentation of sage habitat and invasion of non-native plants can negatively impact this species. Fragmentation increases habitat edges which can result in an increase in predation and parasitism. Non-native vegetation can reduce food availability.

The continued conversion and fragmentation of sagebrush habitats will likely result in a decline in Sage Thrasher populations.