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

Western Tanager Population Trend in Colorado

All statesGeneralists

Western Tanager in Colorado has surged: up 122% on the route-weighted index since 1970.

+122%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 →
91Routes 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 ColoradoNotable 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 Colorado: up 121% on the route-weighted index since 1970.

Western Tanager Population Forecast in Colorado

If the recent trend holds, Western Tanager in Colorado is projected to fall about 19% by 2029 — from 5.4 in 2024 to a central estimate of 4.4 (95% range 2.9–6.0). A 5-year backtest shows a typical error of ±16.2%, with 80% of held-out values landing inside the 95% band.

-19%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 →
4.4Projected 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 →
2.9–6.095% 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 →
±16.2%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 Colorado is projected to fall about 19% by 2029 — from 5.4 in 2024 to a central estimate of 4.4 (95% range 2.9–6.0). A 5-year backtest shows a typical error of ±16.2%, with 80% 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 →
20254.22.65.7
20264.22.75.8
20274.32.75.9
20284.42.85.9
20294.42.96.0

Western Tanager Survey Routes in Colorado

Routes recording Western Tanager in Colorado.
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 →
Buffalo Park5120231992
Dolores Riv4020241988
Mcphee Res.3620241996
South Fork2720241994
Dunckley Pas2420241992
Baxter Pass2320241994
Heeney2220192017
Douglas Pass2120241987
Cheesman Lk2120241969
Fox Creek1920241993
Comanche Pk1920241994
Moon Pass1920241998
Mesaverde Np1820241997
Lake City 21720242017
Haycamp Mesa1720241998
Cokedale1620241995
Marshall Pas1620191995
Owl Creek Pass1620241998
Castleton1520241988
Powderhorn1420231995
Gribbles Prk1320241999
Groundhog Rs1220241995
Wilson Creek1120241995
Walsenburg1120241994
Delta1020211973

Western Tanager Population Trend in Other States

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