Sage Thrasher (Oreoscoptes montanus): COSEWIC rapid review of classification 2021

Official title: COSEWIC Rapid Review of Classification on the Sage Thrasher (Oreoscoptes montanus) in Canada

Committee on the Status of Endangered Wildlife in Canada (COSEWIC)
Endangered 2021

COSEWIC assessment summary

Assessment summary – November 2021

Common name: Sage Thrasher

Scientific name: Oreoscoptes montanus

Status: Endangered

Reason for designation: This songbird is restricted to small areas of southern British Columbia, Alberta, and Saskatchewan, where it is closely associated with remnant sagebrush grasslands. Its distribution and abundance in Canada appear to have been stable over the past decade, but the population remains very small, with an estimated total of 7 to 36 mature individuals. Immigration from small and declining subpopulations in Washington and Montana is likely insufficient to increase the Canadian population. Loss of sagebrush-dominated habitat to residential development, agricultural development, and fire is believed to have resulted in population declines. Climate change presents a growing concern.

Occurrence: British Columbia, Alberta, Saskatchewan

Status history: Designated Endangered in April 1992. Status re-examined and confirmed in November 2000, November 2010, and December 2021.

COSEWIC rapid review of classification

Preface

Since the status of Sage Thrasher was last assessed (COSEWIC 2010), a Recovery Strategy has been produced (Environment Canada 2014b). It did not include a formal threats assessment, but did consider recovery to be feasible and offered a partial description of Critical Habitat. Documentation of Sage Thrasher occurrences in Canada has improved somewhat since the previous assessment, through increased search effort such as the Species at Risk Partnership on Agricultural Lands (Artuso pers. comm. 2021). Information on habitat trends also continues to improve, largely because of interest in other species at risk that share sagebrush habitat, especially Greater Sage-Grouse, Centrocercus urophasianus (Carlisle et al. 2018; Dinkins and Beck 2019; Timmer et al. 2019).

Sage Thrasher continues to be observed in Canada in small numbers annually. Targeted surveys at breeding sites in British Columbia (White Lake, Kilpoola, and Chopaka) in June 2017 yielded one detection (Gross pers. comm. 2021). However, no systematic repeated surveys have been undertaken since the last status report, and sightings in Canada, including breeding records, remain few. For example, over the past ten years, eBird (2021), a citizen science database of bird sightings, shows only 120 breeding season (May-August) reports (excluding each year’s reports within 50 m of each other), with over 80 of them in the Okanagan Valley of British Columbia (eBird 2021). Since the last status report, Saskatchewan’s Conservation Data Centre has added only two records (both singing males; Kusch pers. comm. 2021), and the first four years of the provincial breeding bird atlas have to date produced only three confirmed or possible breeding records (Birds Canada 2020). All recent records have been in areas identified in the previous status report and recovery strategy (COSEWIC 2010; Environment Canada 2014b).

Status history

Designated Endangered in April 1992. Status re-examined and confirmed in November 2000, November 2010, and December 2021.

Updated map

Not required, as no change in distribution is known (Environment Canada 2014b; eBird 2020); see previous assessment (COSEWIC 2010).

Technical summary

Oreoscoptes montanus
Sage Thrasher
Moqueur des armoises
Range of occurrence in Canada (province/territory/ocean): British Columbia, Alberta, Saskatchewan

Demographic information

Generation time (usually average age of parents in the population)

Approximately 2.5 years, based on IUCN estimate (Bird et al. 2020).

Is there an [observed, inferred, or projected] continuing decline in number of mature individuals?

Unknown; no indication of decline, although sightings remain too scarce to reliably estimate trends (eBird 2020).

Estimated percent of continuing decline in total number of mature individuals within [5 years or 2 generations, whichever is longer up to a maximum of 100 years]

Unknown; no indication of decline, although sightings are too scarce to reliably estimate trends.

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over the last [10 years, or 3 generations, whichever is longer up to a maximum of 100 years].

Unknown; no indication of decline, although sightings are too scarce to reliably estimate trends.

[Projected or suspected] percent [reduction or increase] in total number of mature individuals over the next [10 years, or 3 generations, whichever is longer up to a maximum of 100 years].

Unknown; population too small to reliably predict effects of threats.

[Observed, estimated, inferred, or suspected] percent [reduction or increase] in total number of mature individuals over any period [10 years, or 3 generations, whichever is longer up to a maximum of 100 years], including both the past and the future.

Unknown; no indication of decline or prediction of future effects of threats, given limited data on small population.

Are the causes of the decline clearly understood?

Unknown; unclear whether population is declining, but if it is, causes are not clearly understood.

Have the causes of the decline ceased?

Unknown; unclear whether population is declining, but if it is, causes have likely not ceased.

Are the causes of the decline clearly reversible?

Unknown

Are there extreme fluctuations in number of mature individuals?

No

Extent and occupancy information

Estimated extent of occurrence (EOO)

4500 km², based on convex polygon around sites in British Columbia, Alberta, and Saskatchewan that have been occupied at some point between 1990 and 2020; current value could potentially be somewhat smaller.

Index of area of occupancy (IAO), reported as 2x2 km grid value.

40 km², based on 2x2 km grid over sites where breeding occurred between 1990 and 2010 (COSEWIC 2010) or more recently (Birds Canada 2020).

Is the population “severely fragmented” i.e., is >50% of its total area of occupancy in habitat patches that are (a) smaller than would be required to support a viable population, and (b) separated from other habitat patches by a distance larger than the species can be expected to disperse?

No

Number of “locations”^* (use plausible range to reflect uncertainty if appropriate)

At most 9; likely 5 or fewer in at least some years. The species occurs annually at three sites in British Columbia (White Lake, Chopaka, and Kilpoola), each of which is individually vulnerable to the recurrent threat of wildfires (Harrison, pers. comm. 2020). The Sage and Sparrow Grasslands in British Columbia are also likely occupied annually. Up to four locations have been recorded in a given year in Alberta and Saskatchewan (Artuso pers. comm. 2021; Liccioli pers. comm. 2021), although COSEWIC (2010) considered these to comprise a single location.

Is there an [observed, inferred, or projected] continuing decline in extent of occurrence?

No, all locations identified in the status report (COSEWIC 2010) remain in use.

Is there an [observed, inferred, or projected] continuing decline in index of area of occupancy?

No

Is there an [observed, inferred, or projected] continuing decline in number of subpopulations?

No

Is there an [observed, inferred, or projected] continuing decline in number of “locations”^*?

No, all locations identified in the status report (COSEWIC 2010) remain in use.

Is there an [observed, inferred, or projected] continuing decline in [area, extent and/or quality of] habitat?

Yes, observed decline in area and quality of breeding habitat in the Okanagan and Similkameen valleys of British Columbia, and likely declines in area and quality of habitat in Alberta and Saskatchewan (COSEWIC 2010; Environment Canada 2014b).

Improvement of habitat for Greater Sage-Grouse, ongoing in Alberta and Saskatchewan (Environment Canada 2014a), may improve habitat for Sage Thrasher according to some studies (Timmer et al. 2019), but not others (Carlisle et al. 2018; Dinkins and Beck 2019).

Are there extreme fluctuations in number of subpopulations?

No

Are there extreme fluctuations in number of “locations”^*?

No

Are there extreme fluctuations in extent of occurrence?

No

Are there extreme fluctuations in index of area of occupancy?

No

^* See Definitions and Abbreviations on COSEWIC website and IUCN for more information on this term.

Number of mature individuals (in each subpopulation)

Quantitative analysis

Is the probability of extinction in the wild at least [20% within 20 years or 5 generations whichever is longer up to a maximum of 100 years, or 10% within 100 years]? Unknown; analysis not conducted.

Threats and limiting factors

Was a threats calculator completed for this species? No, but threats identified in COSEWIC (2010) were ranked in the Recovery Strategy (Environment Canada 2014b)

Overall threat impact: High (based on Environment Canada 2014b)

Threats identified in the Recovery Strategy (Environment Canada 2014b) are:

High concern:

• IUCN 1 (Residential and commercial development): habitat loss from housing and urban areas (1.1), commercial and industrial areas (1.2), tourism and recreation areas (1.3)
• IUCN 2 (Agriculture and aquaculture): habitat loss from annual and perennial non-timber crops (2.1), livestock farming and ranching (2.3)
• IUCN 7 (Natural systems modifications): habitat loss from fire (7.1)

Medium concern:

• IUCN 4 (Transportation and service corridors): habitat loss to roads (4.1), utility and service lines (4.2)
• IUCN 3 (Energy production and mining): habitat loss to oil and gas drilling (3.1), mining and quarrying (3.2)

Low concern:

• IUCN 11 (Climate change and severe weather): mortality from temperature extremes (11.3)

Recent habitat modeling suggests that climate change may exacerbate other habitat-related threats (Millikin et al. 2020).

What additional limiting factors are relevant? The population is mainly limited by availability of suitable sagebrush habitat (COSEWIC 2010; Environment Canada 2014b).

Rescue effect (natural immigration from outside Canada)

Status of outside population(s) most likely to provide immigrants to Canada.

Assessed as S2 (Imperilled) in Washington State and S3 (Vulnerable) in Montana, and global rank was been reduced to G4 (Apparently Secure) in 2016 (NatureServe 2021). At low densities and likely declining in the Columbia Plateau of the United States, which is the presumed source of most birds in Canada. Most recent 10-year trend available from the Breeding Bird Survey (BBS) for Bird Conservation Region 9 (which includes the Columbia Plateau) is -1.2% per year (95% CI -3.2, 0.5; Smith pers. comm. 2020).

Is immigration known or possible?

Yes, Canada’s population is likely sustained by immigration from the United States (Environment Canada 2014b).

Would immigrants be adapted to survive in Canada?

Yes, successful breeding of presumed immigrants occurs in suitable habitat.

Is there sufficient habitat for immigrants in Canada?

Yes, but limited in extent. Sagebrush habitat persists and is the focus of conservation efforts, especially for Greater Sage-Grouse in Alberta and Saskatchewan (Environment Canada 2014a) and some parcels acquired for protection in southern British Columbia.

Are conditions deteriorating in Canada?⁺

Yes, threats to habitat rated as “continuing” in recovery strategy (Environment Canada 2014b)

Are conditions for the source (i.e., outside) population deteriorating?⁺

Yes, BBS shows declines in source population (see above), whose habitat is under threats (Environment Canada 2014a,b).

Is the Canadian population considered to be a sink?⁺

Unknown. Immigration from the United States may contribute to the Canadian population (see above), but it is unclear whether the Canadian population is a sink.

Is rescue from outside populations likely?

Unknown. Immigration is probably already contributing to the population, but is unlikely to be sufficient to recover it, given continuing threats to habitat and a declining source population.

⁺ See Table 3 (Guidelines for modifying status assessment based on rescue effect).

Occurrence data sensitivity

Are occurrence data of this species sensitive? No

Status history

COSEWIC: Designated Endangered in April 1992. Status re-examined and confirmed in November 2000, November 2010, and December 2021.

Status and reasons for designation

Status: Endangered

Alpha-numeric codes: B1ab(iii)+2ab(iii); D1

Reasons for designation: This songbird is restricted to small areas of southern British Columbia, Alberta, and Saskatchewan, where it is closely associated with remnant sagebrush grasslands. Its distribution and abundance in Canada appear to have been stable over the past decade, but the population remains very small, with an estimated total of 7 to 36 mature individuals. Immigration from small and declining subpopulations in Washington and Montana is likely insufficient to increase the Canadian population. Loss of sagebrush-dominated habitat to residential development, agricultural development, and fire is believed to have resulted in population declines. Climate change presents a growing concern.

Applicability of criteria

Criterion A (Decline in Total Number of Mature Individuals): Not applicable. Insufficient data to reliably infer, project, or suspect population trends.

Criterion B (Small Distribution Range and Decline or Fluctuation): Meets Endangered, B1ab(iii) and B2ab(iii), based on EOO of 4500 km², IAO of 40 km², fewer than five locations, and an observed decline in extent and quality of habitat.

Criterion C (Small and Declining Number of Mature Individuals): Not applicable. Number of mature individuals (7-36) is below the threshold for Endangered. However, there is no evidence of continuing decline in the number of mature individuals.

Criterion D (Very Small or Restricted Population): Meets D1, Endangered. Number of mature individuals estimated to be 7-36.

Criterion E (Quantitative Analysis): Analysis not conducted.

Acknowledgements

Funding for the preparation of this report was provided by Environment and Climate Change Canada. The authorities listed below provided valuable data and/or advice.

Authorities contacted

Artuso, C. Wildlife Biologist, Canadian Wildlife Service, Environment and Climate Change Canada, Gatineau, Quebec.

Court, G. Provincial Wildlife Status Biologist, Fish and Wildlife Management, Alberta Environment and Parks, Edmonton, Alberta.

Fisher, R. Curator of Vertebrate Zoology, Royal Saskatchewan Museum, Regina, Saskatchewan.

Govindarajulu, P. Unit Head, Species Conservation Science Unit. BC Ministry of Environment and Climate Change Strategy, Victoria, British Columbia.

Gross, E. Senior Species at Risk Biologist. Canadian Wildlife Service, Environment and Climate Change Canada. Delta, British Columbia.

Gutsell, R. Wildlife Status Biologist, Fish and Wildlife Management, Alberta Environment and Parks, Edmonton, Alberta.

Harrison, M. Habitat Stewardship Program Coordinator, Environment and Climate Change Canada, Delta, British Columbia.

Hwang, Y.T. Head, Conservation Planning, Environment and Climate Change Canada, Edmonton, Alberta.

Keith, J. Coordinator, Saskatchewan Conservation Data Centre, Fish, Wildlife and Lands Branch, Saskatchewan Ministry of Environment, Regina, Saskatchewan.

Knapton, R. Biologist, Ottawa, Ontario.

Kusch, J. Zoologist, Saskatchewan Conservation Data Centre, Regina, Saskatchewan.

Liccioli, S. Ecosystem Scientist. Grasslands National Park, Parks Canada Agency, Val Marie, Saskatchewan.

Mahony, N. Research Biologist, Environment and Climate Change Canada. Edmonton, Alberta.

Neufeld, C. Grassland Ecologist, Environment and Climate Change Canada, Saskatoon, Saskatchewan.

Pietro Diaz, B. Terrestrial Ecologist, Habitat Unit, Fish, Wildlife and Lands Branch, Saskatchewan Ministry of Environment, Regina, Saskatchewan.

Information sources

Artuso, C., pers. comm. 2021. Email correspondence to A.G. Horn. February 2021. Wildlife Biologist. Canadian Wildlife Service, Environment and Climate Change Canada, Gatineau, Quebec.

Bird, J., R. Martin, H.R. Akçakaya, J. Gilroy, I.J. Burfield, S.T. Garnett, A. Symes, J. Taylor, C.H. Şekercioğlu, and S.H.M. Butchart. 2020. Generation lengths of the world’s birds and their implications for extinction risk. Conservation Biology 34:1252–1261.

Birds Canada. 2020. Species Highlights for 2020. Saskatchewan Breeding Bird Atlas Fall Newsletter 2020: 4. Website: [accessed November 2020].

Carlisle, J.D, A.D. Chalfoun, K.T. Smith, and J.L. Beck. 2018. Nontarget effects on songbirds from habitat manipulation for Greater Sage-Grouse: implications for the umbrella species concept. Condor: Ornithological Applications 120:439-455.

COSEWIC. 2010. Update COSEWIC Status Report on Sage Thrasher (Oreoscoptes montanus). Committee on the Status of Endangered Wildlife in Canada. Ottawa, Ontario.

Dinkins, J.B., and J.L. Beck. 2019. Comparison of conservation policy benefits for an umbrella and related sagebrush-obligate species. Human–Wildlife Interactions 13:447–458.

eBird. 2021. eBird: An online data base of bird distribution and abundance [web application]. eBird, Ithaca, New York. Website: [accessed October 2021].

Environment Canada. 2014a. Amended Recovery Strategy for the Greater Sage-Grouse (Centrocercus urophasianus urophasianus) in Canada. Species at Risk Act Recovery Strategy Series. Environment Canada, Ottawa. vi + 53 pp.

Environment Canada. 2014b. Recovery Strategy for the Sage Thrasher (Oreoscoptes montanus) in Canada. Species at Risk Act Recovery Strategy Series. Environment Canada, Ottawa. iv + 30 pp.

Gross, E., pers. comm. 2021. Email correspondence to A.G. Horn. May 2021. Senior Species at Risk Biologist. Canadian Wildlife Service, Environment and Climate Change Canada. Delta, British Columbia.

Harrison, M., pers. comm. 2020. Email correspondence to A.G. Horn. August 2020. Habitat Stewardship Program Coordinator. Environment and Climate Change Canada, Delta, British Columbia.

Kusch, J., pers. comm. 2020. Email correspondence to A.G. Horn. August 2020. Zoologist, Saskatchewan Conservation Data Centre, Regina, Saskatchewan.

Liccioli, S., pers. comm. 2021. Email correspondence to A.G. Horn. April 2021. Ecosystem Scientist. Grasslands National Park, Parks Canada Agency, Val Marie, Saskatchewan.

Millikin, R., R. Joy, J. Komaromi, M. Harrison, N. A. Mahony, and W. M. Vander Haegen. 2020. Recovery of peripheral Sage Thrashers under climate change. Conservation Science and Practice 2020;e290.

NatureServe. 2021. NatureServe Explorer: An online encyclopedia of life [web application]. NatureServe, Arlington, Virginia. Website: [accessed October 2021].

Sauer, J.R., D.K. Niven, J.E. Hines, D.J. Ziolkowski, Jr., K.L Pardieck, J.E. Fallon, and W.A. Link. 2017. The North American Breeding Bird Survey, Results and Analysis 1966-2015. Version 02.07.2017. USGS Patuxent Wildlife Research Center, Laurel, Maryland.

Smith, A., pers. comm. 2020. Email correspondence with M. Gahbauer. May 2021. Senior Biostatistician, Canadian Wildlife Service, Environment and Climate Change Canada, Ottawa, Ontario.

Timmer, J.M., C.L. Aldridge, and M.E. Fernández‐Giménez. 2019. Managing for multiple species: greater sage‐grouse and sagebrush songbirds. Journal of Wildlife Management 83:1043-1056.

Writer of rapid review of classification

Andrew G. Horn

COSEWIC history

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2021)

Wildlife species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed.

Special concern (SC)
(Note: Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.)

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at risk (NAR)
(Note: Formerly described as “Not In Any Category”, or “No Designation Required.”)

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data deficient (DD)
(Note: Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” [insufficient scientific information on which to base a designation] prior to 1994. Definition of the [DD] category revised in 2006.)

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

The Canadian Wildlife Service, Environment and Climate Change Canada, provides full administrative and financial support to the COSEWIC Secretariat.