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

Western Tanager Population Trend in Montana

All statesGeneralists

Western Tanager in Montana has surged: up 235% on the route-weighted index since 1970.

+235%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 →
69Routes 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 Western Tanager 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 →

Western Tanager has surged in Montana: up 235% on the route-weighted index since 1970.

Western Tanager Population Forecast in Montana

If the recent trend holds, Western Tanager in Montana is projected to stay roughly flat through 2029, near 6.2 (95% range 4.4–7.9). A 5-year backtest shows a typical error of ±7.2%, with 100% of held-out values landing inside the 95% band.

+6%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 →
6.2Projected 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 →
4.4–7.995% 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 →
±7.2%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, Western Tanager in Montana is projected to stay roughly flat through 2029, near 6.2 (95% range 4.4–7.9). A 5-year backtest shows a typical error of ±7.2%, 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 →
20255.94.17.7
20266.04.27.7
20276.04.37.8
20286.14.37.9
20296.24.47.9

Western Tanager Survey Routes in Montana

Routes recording Western Tanager 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 →
Threemile Wa4220241993
Greenoagh 33820242012
Woodman3120241968
Cramer Creek3020191994
Elevation Mt2920241995
Whitefish Lake2920242016
Painted Rock2720221992
St Regis2520241977
Swan Lake2520242015
Greenoagh 22520112005
Skalkaho2519981992
Red Rock2420241981
Thompson Riv2420241993
Hebgen Lake2420242017
Skalkho-Rye2220221999
Fish Creek2220241995
Libby Dam2020241979
Clinton1920241972
Maynard Coulee1720242017
Noxon1520231995
Arlee1420241968
Sula1420241977
Pryor Mtn.1320241995
East Glacier Park1120242015
Victor1020241993

Western Tanager Population Trend in Other States

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