Brewer's Sparrow - Spizella breweri
State Rank Reason (see State Rank above)
Species faces threats from loss of sagebrush habitats it is dependent on as a result of habitat conversion for agriculture and increased frequency of fire as a result of weed encroachment and drought.
- Details on Status Ranking and Review
ScoreU - Unknown
ScoreG - 200,000-2,500,000 km squared (about 80,000-1,000,000 square miles)
Comment380,531 square kilometers based on Natural Heritage Program range maps that appear on the Montana Field Guide
Area of Occupancy
ScoreU - Unknown
ScoreD - Moderate Decline (decline of 25-50%)
CommentSagebrush cover drastically reduced in Montana (25-50% decline) since European arrival.
ScoreE - Stable. Population, range, area occupied, and/or number or condition of occurrences unchanged or remaining within ±10% fluctuation
CommentBBS data for Montana is of highest credibility and shows a +0.7% increase per year or 7% decline per decade. Recent slight increases or declines for most surrounding states and provinces.
ScoreB - Moderate and imminent threat. Threat is moderate to severe and imminent for a significant proportion (20-60%) of the population or area.
CommentHabitat loss from agriculture, energy development and increased fire frequency resulting from weeds probably represent the greatest threats to the species.
SeverityModerate - Major reduction of species population or long-term degradation or reduction of habitat in Montana, requiring 50-100 years for recovery.
CommentIt takes a very long time for sagebrush communities to recover 30+ years.
ScopeModerate - 20-60% of total population or area affected
CommentFire as a result of weed encroachment on sagebrush communities represents a threat across large portions (20-60%) of the landscape.
ImmediacyModerate - Threat is likely to be operational within 2-5 years.
CommentOngoing and accelerating
ScoreC - Not Intrinsically Vulnerable. Species matures quickly, reproduces frequently, and/or has high fecundity such that populations recover quickly (< 5 years or 2 generations) from decreases in abundance; or species has high dispersal capability such that extirpated populations soon become reestablished through natural recolonization (unaided by humans).
ScoreB - Narrow. Specialist. Specific habitat(s) or other abiotic and/or biotic factors (see above) are used or required by the Element, but these key requirements are common and within the generalized range of the species within the area of interest.
CommentNarrow Specialist. Species is a sagebrush obligate.
Raw Conservation Status Score
3.5 + 0.0 (geographic distribution) + 0.0 (environmental specificity) + 0.0 (short-term trend) - 0.75 (threats) = 2.75
How Scores are Calculated
The Brewer's Sparrow is a nondescript sparrow of sagebrush habitats. In suitable habitat, the Brewer's Sparrow can be the most abundant species present. Its song, a series of distinctive long and short buzzy trills, can be heard throughout the breeding season (Rotenberry et al. 1999).
Arrives on breeding grounds by late April. Nests with eggs observed as early as late May. Nestlings observed as early as early June and fledglings by early July (Montana Natural Heritage Program Point Observation Database 2014).
Sexes are similar in appearance. The crown is finely streaked brown; pale gray eyebrow, complete white eye-ring, and a grayish mustache. Underparts dull white, with grayish flanks; breast unstreaked in adult, although sometimes flanks are streaked. Back and rump brown, the latter streaked with black (Rotenberry et al. 1999).
Western Hemisphere Range
The Brewer's Sparrow occurs throughout Montana during the breeding season in appropriate sagebrush habitats.
Summary of Observations Submitted for Montana
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(direct evidence "B")
(indirect evidence "b")
No evidence of Breeding
(regular observations "W")
(at least one obs. "w")
(Records associated with a range of dates are excluded from time charts)
Spring arrival records in Montana in mid- to late-April (Montana Natural Heritage Program Point Observation Database 2014). Fall movements from August to early October.
The Brewer's Sparrow typically breeds in shrubsteppe habitats dominated by sagebrush. Densities of Brewer's Sparrow correlated with some aspect of total shrub cover (Rotenberry et al. 1999). In sagebrush areas in central Montana, Brewer's Sparrows nested in sagebrush averaging 16 inches high (Best 1970).
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:
- 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);
- Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
- Examining the observation records for each species in the state-wide point database associated with each ecological system;
- 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 email@example.com
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.
- 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.
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Shrubland, Steppe and Savanna Systems
- Occasionally Associated with these Ecological Systems
Forest and Woodland Systems
Wetland and Riparian Systems
The Brewer's Sparrow eats primarily insects during the breeding season, and young are fed almost exclusively arthropods (Rotenberry et al. 1999). Foraging occurs primarily in shrubs. In central Montana, food volume was 71 to 81% animal (Coeopterans and Hemipterans) and 8 to 17% plant (grass seeds), although chemical spraying may have led to a greater dependence on plants (Best 1970).
In central Montana, an average of 37 breeding pairs were found per 100 acres. This species is frequently parasitized by the Brown-headed Cowbird but depends upon size of nearby cowbird populations (Rotenberry et al. 1999).
In central Montana, 74% of nests were found between 6 to 8 inches above the ground in big sagebrush (Davis 1961). Clutch size is 3-4 eggs. Females primarily incubate, with the incubation period averaging 11 days (range 10-12 days). Some evidence that males also incubate. Nestling period 6-9 days after eggs hatch. Both parents feed fledged young for at least several days after fledging (Rotenberry et al. 1999).
Management activities that result in a reduction of sagebrush reduces breeding populations of Brewer's Sparrow. Re-seeding areas with non-native bunchgrasses such as crested wheatgrass degrades habitat quality for this species. Additionally, areas affected by cheatgrass can experience increased frequency and severity of fires, which can reduce or eliminate sagebrush (Hansley and Beauvais 2004). The recent Greater Sage-Grouse Habitat Conservation Strategy
developed for Montana may also assist in the conservation and management of other sagebrush-dependent species, including the Brewer's Sparrow.
Threats or Limiting Factors
The primary threat to Brewer's Sparrow breeding populations is fragmentation and loss of sagebrush shrublands and shrub-steppe habitats (Rotenberry et al. 1999).
- Literature Cited AboveLegend: View WorldCat Record View Online Publication
- Best, L.B. 1970. Effects of ecological changes induced by various sagebrush control techniques on non-game birds. M.S. thesis. Montana State University, Bozeman. 74pp.
- Davis, C.V. 1961. A distributional study of the birds of Montana. Ph.D. dissertation. Oregon State University, Corvallis. 462 pp.
- Rotenberry, J. T., M. A. Patten, and K. L. Preston. 1999. Brewer's sparrow (Spizella breweri). In: A. Poole and F. Gill, eds. The Birds of North America, Number 390. The Birds of North America, Inc., Philadelphia, PA. 24 pp.
- Skaar, P.D. 1969. Birds of the Bozeman latilong: a compilation of data concerning the birds which occur between 45 and 46 N. latitude and 111 and 112 W. longitude, with current lists for Idaho, Montana, Wyoming, impinging Montana counties and Yellowstone National Park. Bozeman, MT. 132 p.
- Additional ReferencesLegend: View WorldCat Record View Online Publication
Do you know of a citation we're missing?
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