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

Western Tanager Population Trend in Idaho

All statesGeneralists

Western Tanager in Idaho has surged: up 362% on the route-weighted index since 1971.

+362%Since 1971TrendPercent 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 →
60Routes 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 →
55YearsYears 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 IdahoNotable 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 Idaho: up 362% on the route-weighted index since 1971.

Western Tanager Population Forecast in Idaho

If the recent trend holds, Western Tanager in Idaho is projected to stay roughly flat through 2029, near 9.4 (95% range 6.6–12). A 5-year backtest shows a typical error of ±16.5%, with 100% of held-out values landing inside the 95% band.

-2%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 →
9.4Projected 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 →
6.6–1295% 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 →
±16.5%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 Idaho is projected to stay roughly flat through 2029, near 9.4 (95% range 6.6–12). A 5-year backtest shows a typical error of ±16.5%, 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 →
20258.96.112
20269.06.212
20279.16.412
20289.36.512
20299.46.612

Western Tanager Survey Routes in Idaho

Routes recording Western Tanager in Idaho.
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 →
Cascade5419841968
Cobalt4720241989
Deep Creek4419851985
Rochat Divde3920231993
Cabarton3820231985
Grangeville3320241986
Coolin3320241986
Pierce2820071990
Mivoden2520231977
Lolo Pass2320191992
Featherville2120241989
Cape Horn2020241986
Salmon River2020211988
Avery1920231979
Sunbeam1920191994
Silver City1920241989
N Fork Cda R1820191993
Centerville1720191972
Marble Creek1720231988
Squirrel1620241971
Yellow Pine1520161989
Sawtooth Cty1320141988
Baldy Mountain1220162013
Challis1120241976
Alturas1019871968

Western Tanager Population Trend in Other States

alaskaarizonacaliforniacoloradomontananebraskanevadanew-mexicooregonsouth-dakotatexasutahwashingtonwyoming

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