BirdAnalyst
Species · Montana · BBS 2026 Release · 1966–2025

Brewer's Sparrow Population Trend in Montana

All statesArid-land birds

Brewer's Sparrow in Montana has edged down: down 22% on the route-weighted index since 1970.

-22%Since 1970TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
85Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
57YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Brewer's Sparrow Trends in MontanaNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

No notable trend signals for Brewer's Sparrow in Montana. See the full index history below.

Brewer's Sparrow Population Forecast in Montana

If the recent trend holds, Brewer's Sparrow in Montana is projected to fall about 39% by 2030 — from 5.6 in 2025 to a central estimate of 3.4 (95% range 0.00–7.1). A 5-year backtest shows a typical error of ±15.7%, with 100% of held-out values landing inside the 95% band.

-39%Change by 2030TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
3.4Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–7.195% range95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
±15.7%Backtest errorBacktest errorTypical error when we hold out the most recent years, forecast them, and compare to what actually happened. Lower means a more trustworthy projection.Full methodology →
If the recent trend holds, Brewer's Sparrow in Montana is projected to fall about 39% by 2030 — from 5.6 in 2025 to a central estimate of 3.4 (95% range 0.00–7.1). A 5-year backtest shows a typical error of ±15.7%, with 100% of held-out values landing inside the 95% band.19682030
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →95% low95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →95% high95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
20263.50.007.2
20273.50.007.2
20283.50.007.1
20293.40.007.1
20303.40.007.1

Brewer's Sparrow Survey Routes in Montana

Routes recording Brewer's Sparrow in Montana.
Recent countThe raw number of individuals recorded on this route in its most recent survey year. A single-route tally, not a trend.Full methodology →
Beaverhead6720251973
Custer 25620252024
Red Rock5320251973
Custer3720222019
Boulder3120251969
Lima3020251995
Brunzell Slough2520252015
Willow Creek 22220251982
Roundup2020252016
Powderville1920251968
Leroy1720251970
Winnett1420252017
Hebgen Lake1420252017
Flatwillow 21320232011
Chinook1320252017
Pryor Mtn.1320251995
Two Dot1020091976
Ingomar1020231968
Freeman Creek1020162015
Albion920251982
Clyde Park920252018
Harlem820211968
Malta820251975
Brusett720241983
Wheat Basin720252017

Brewer's Sparrow Population Trend in Other States

arizonacaliforniacoloradoidahokansasnebraskanevadanew-mexiconorth-dakotaoklahomaoregonsouth-dakotatexasutahwashingtonwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.