Species and Plant Community
Accounts for Identified Wildlife

Table of contents

SAGE THRASHER (Oreoscoptes montanus)

Status

The sage thrasher is RED-listed and listed as ENDANGERED by COSEWIC because of very low, variable abundance. It is restricted to a handful of breeding sites in a small area of the province.

Ecology

The sage thrasher is a robin-sized member of the mockingbird family. It breeds in large tracts of big sagebrush (Artemesia tridentata), arriving in B.C. in May and departing from late August to early September. From observations taken over the 1993 and 1994 breeding season, this species seems to select pockets of big sturdy sage surrounded by open areas of perennial grasses, important for feeding. The best nesting sites have higher grass cover, particularly perennial grass, significantly lower rock cover and a lower cattle feces cover. Sagebrush near historical and current nests is more evenly dispersed than in areas not used for nesting. A moderate percent cover of sage seems to be preferable for nest sites, an observation that is concurrant with findings in Washington state.

Distribution

Ecoprovince: Ecosections

Biogeoclimatic unit

Breeding range

British Columbia represents the northern-most extension of the breeding range of sage thrashers. In B.C., they regularly breed only in two or three localities in the south Okanagan and Similkameen valleys: 1) along the Nighthawk Road near the Chopaka Customs station; 2) in the Richter Pass/Kilpoola Lake area; and 3) at White Lake, west of Okanagan Falls. Vagrant near the coast, records (probably extralimital) of singing males have been documented as far north as Spences Bridge, near the Lytton area, Lac du Bois (Kamloops) and Vernon.

Nonbreeding range

The nonbreeding range is the same as the breeding range.

Wintering and migration

Sage thrashers winter in the southwestern U.S. and Mexico.

Habitat requirements

Broad ecosystem unit

Structural stage

2 and 3a: herb and low shrub (<3 m)

Critical habitats and habitat features

Sage thrashers nest in large, tall and sturdy sagebrush (sagebrush of 1m, average nest bush size 123 cm) in areas with a moderate dispersion of sage (16% total cover of sage). Individuals select sage bushes that have the greatest total height (mean of 132 cm) and crown width (168 cm) and have a full crown (i.e., no gaps) for nesting. In one study, all nest bushes were 75% or more live and had few gaps in either the vertical or horizontal profile.

Selected references

Cannings, R.J. 1991. Status report on the sage thrasher, in British Columbia. B.C. Min.
Environ., Wildl. Br., Victoria, B.C. Wildl. Bull. No. B-79.

Dobler, F.C. 1992. Washington State shrub steppe ecosystem studies: with emphasis on
avian species occurrence, densities and diversity. Paper presented at Northwest Scientific Association Annual Meeting, 1992, Bellingham, WA.

Millikin, R.L., S. McConnell and R. van der Driessche. [In prep]. Habitat selection by
sage thrashers in British Columbia. Can. Wildl. Serv., Delta, B.C.

Rich, T. 1978. Nest placement in sage thrashers. Wilson Bull. 90: 303.


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