BirdAnalyst
Species · Montana · BBS 2025 Release · 1966–2024

Great Blue Heron Population Trend in Montana

All statesWetland birds

Great Blue Heron in Montana has fallen sharply: down 57% on the route-weighted index since 1970.

-57%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 →
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 Great Blue Heron 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 →

Great Blue Heron has fallen sharply in Montana: down 57% on the route-weighted index since 1970.

Great Blue Heron Population Forecast in Montana

If the recent trend holds, Great Blue Heron in Montana is projected to fall about 25% by 2029 — from 0.38 in 2024 to a central estimate of 0.28 (95% range 0.00–0.66). A 5-year backtest shows a typical error of ±20.4%, with 100% of held-out values landing inside the 95% band.

-25%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 →
0.28Projected 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 →
0.00–0.6695% 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 →
±20.4%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, Great Blue Heron in Montana is projected to fall about 25% by 2029 — from 0.38 in 2024 to a central estimate of 0.28 (95% range 0.00–0.66). A 5-year backtest shows a typical error of ±20.4%, 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 →
20250.320.000.69
20260.310.000.68
20270.300.000.67
20280.290.000.67
20290.280.000.66

Great Blue Heron Survey Routes in Montana

Routes recording Great Blue Heron 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 →
St Xavier1020101980
Brandenberg620151969
Chinook620222018
Pablo Res.420241995
East Glacier Park420242017
Glasgow320241968
Webster320161985
Laurel320221968
Church Hill320242017
Arlee220241970
Great Falls220161973
Flatwillow220081970
Forsyth220181980
Willow Creek219811974
Powderville220221979
Thompson Riv219951993
Painted Rock220161993
Noxon219981998
Swan Lake220182018
Lindsay220182015
Clancy220172015
Hebgen Lake220232017
Pryor Mtn.220152000
Fort Logan220242024
Libby Dam120111983

Great Blue Heron Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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