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Species · Montana · BBS 2025 Release · 1966–2024

Brewer's Blackbird Population Trend in Montana

All statesGeneralists

Brewer's Blackbird in Montana has fallen sharply: down 55% on the route-weighted index since 1970.

-55%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 →
108Routes 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 →
56YearsYears 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 Blackbird 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 →

long arc declinecomputed indexTrend sourceWhether the figure is our own computed route-weighted index or an official USGS modeled estimate. The current build labels every trend as computed.Full methodology →

Brewer's Blackbird has fallen sharply in Montana: down 55% on the route-weighted index since 1970.

Brewer's Blackbird Population Forecast in Montana

If the recent trend holds, Brewer's Blackbird in Montana is projected to fall about 39% by 2029 — from 18 in 2024 to a central estimate of 11 (95% range 1.8–20). A 5-year backtest shows a typical error of ±23.9%, with 100% of held-out values landing inside the 95% band.

-39%Change by 2029TrendPercent 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 →
11Projected 2029 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
1.8–2095% 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 →
±23.9%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 Blackbird in Montana is projected to fall about 39% by 2029 — from 18 in 2024 to a central estimate of 11 (95% range 1.8–20). A 5-year backtest shows a typical error of ±23.9%, with 100% of held-out values landing inside the 95% band.19682029
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 →
2025122.921
2026122.621
2027122.321
2028112.120
2029111.820

Brewer's Blackbird Survey Routes in Montana

Routes recording Brewer's Blackbird 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 →
Twin Bridges10219761968
St Mary10020081968
Lambert10020242021
Savage7020211969
Whitlash6720242009
St. Mary 26320242009
Glasgow5820241968
Hay Lake5720221988
Fort Logan5720242018
Raynesford5420242016
Reed Point5220241977
Cabin Creek5220242019
Albion5120241982
Clyde Park5020242018
Polson4920241972
Augusta4520241976
Freeman Creek4220162015
Boulder4120241969
Wolf Creek4120222015
Lindsay3720242015
Harlem3620211968
Saco3320242015
Glentana3120242015
Philipsburg3120242015
Lima3020241994

Brewer's Blackbird Population Trend in Other States

arizonacaliforniacoloradoidahoindianamichiganminnesotanebraskanevadanew-mexiconorth-dakotaoklahomaoregonsouth-dakotatexasutahwashingtonwisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.