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

Bald Eagle Population Trend in Montana

All statesBirds of prey

Bald Eagle in Montana has surged: up 923% on the route-weighted index since 1984.

+923%Since 1984TrendPercent 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 →
61Routes 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 →
37YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Bald Eagle 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 increasecomputed 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 →

Bald Eagle has surged in Montana: up 923% on the route-weighted index since 1984.

Bald Eagle Population Forecast in Montana

If the recent trend holds, Bald Eagle in Montana is projected to fall about 17% by 2030 — from 0.63 in 2025 to a central estimate of 0.52 (95% range 0.26–0.79). A 5-year backtest shows a typical error of ±13.6%, with 100% of held-out values landing inside the 95% band.

-17%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 →
0.52Projected 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 →
0.26–0.7995% 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 →
±13.6%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, Bald Eagle in Montana is projected to fall about 17% by 2030 — from 0.63 in 2025 to a central estimate of 0.52 (95% range 0.26–0.79). A 5-year backtest shows a typical error of ±13.6%, with 100% of held-out values landing inside the 95% band.19692030
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 →
20260.470.210.74
20270.490.220.75
20280.500.230.76
20290.510.240.77
20300.520.260.79

Bald Eagle Survey Routes in Montana

Routes recording Bald Eagle 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 →
Lima3020252009
Pablo Res.520241998
Forsyth320232014
Thompson Riv320232021
Church Hill320252017
Libby Dam220131991
Highwood220232023
Boulder220252016
Red Rock220251994
Greenoagh 2220082008
Brunzell Slough220252022
Hebgen Lake220252017
Kalispell120251984
St Mary120041997
Flatwillow 2120222022
Victor120242024
Virgelle120242021
Cleveland120252024
Cramer Creek120192019
Glen120252000
Glasgow120152015
Willow Creek 2120252024
Polson120241996
Arlee120181969
Augusta120142009

Bald Eagle Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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