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Montana Animal Field Guide

Montana Field Guides

Sage Thrasher - Oreoscoptes montanus

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Species of Concern

Global Rank: G5
State Rank: S3B

Agency Status
USFWS:
USFS:
BLM: SENSITIVE
FWP Conservation Tier: 3
PIF: 3

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Copyright by: The Macaulay Library at the Cornell Lab of Ornithology, Ithaca, NY, all rights reserved.
 
General Description
The Sage Thrasher is unique in being the only thrasher in the genus Oreoscoptes. Genetic work indicates this species may be more closely related to the mockingbirds (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.

Diagnostic Characteristics
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.

General Distribution
Montana Range



Western Hemisphere Range

 


Distribution 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.

Summary of Observations Submitted for Montana
Number of Observations: 693

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density

Recency

Breeding
(direct evidence "B")


Breeding
(indirect evidence "b")


No evidence of Breeding
(transient "t")


Overwintering
(regular observations "W")


Overwintering
(at least one obs. "w")



 

(Records associated with a range of dates are excluded from time charts)



Migration
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.

Habitat
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.

Ecological Systems Associated with this Species
  • Details on Creation and Suggested Uses and Limitations
    How Associations Were Made
    We associated the use and habitat quality (high, medium, or low) of each of the 82 ecological systems mapped in Montana for vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
    1. Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2001, Adams 2003, and Werner et al. 2004);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point database associated with each ecological system;
    4. Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of “observations versus availability of habitat”.
    Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.  In general, species were associated as using an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.  However, species were not associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if point observations were associated with that system.  High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the literature.  The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignments of habitat quality.  If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at bmaxell@mt.gov or (406) 444-3655.

    Suggested Uses and Limitations
    Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.  These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.  Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.  Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.  Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).  Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species’ known geographic range.

    Literature Cited
    • Adams, R.A.  2003.  Bats of the Rocky Mountain West; natural history, ecology, and conservation.  Boulder, CO: University Press of Colorado.  289 p.
    • Dobkin, D. S.  1992.  Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34.  Missoula, MT.
    • Foresman, K.R.  2001.  The wild mammals of Montana.  Special Publication No. 12.  Lawrence, KS: The American Society of Mammalogists.  278 p.
    • Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998.  Montana atlas of terrestrial vertebrates.  Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT.  1302 p.
    • Hutto, R.L. and J.S. Young.  1999.  Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32.  72 p.
    • Maxell, B.A.  2000.  Management of Montana’s amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species.  Report to U.S. Forest Service Region 1.  Missoula, MT: Wildlife Biology Program, University of Montana.  161 p.
    • Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath.  2004.  Amphibians and reptiles of Montana.  Missoula, MT: Mountain Press Publishing Company. 262 p.

Food Habits
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.

Reproductive Characteristics
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.

Management
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.

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

References
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Citation for data on this website:
Sage Thrasher — Oreoscoptes montanus.  Montana Field Guide.  Montana Natural Heritage Program and Montana Fish, Wildlife and Parks.  Retrieved on April 16, 2014, from http://FieldGuide.mt.gov/detail_ABPBK04010.aspx
 
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