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

Black-headed Grosbeak Population Trend in Idaho

All statesGeneralists

Black-headed Grosbeak in Idaho has surged: up 323% on the route-weighted index since 1971.

+323%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 →
53Routes 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 →
54YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Black-headed Grosbeak 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 →

Black-headed Grosbeak has surged in Idaho: up 323% on the route-weighted index since 1971.

Black-headed Grosbeak Population Forecast in Idaho

If the recent trend holds, Black-headed Grosbeak in Idaho is projected to rise about 33% by 2029 — from 1.7 in 2024 to a central estimate of 2.3 (95% range 1.6–3.0). A 5-year backtest shows a typical error of ±15.7%, with 100% of held-out values landing inside the 95% band.

+33%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 →
2.3Projected 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 →
1.6–3.095% 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 →
±15.7%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, Black-headed Grosbeak in Idaho is projected to rise about 33% by 2029 — from 1.7 in 2024 to a central estimate of 2.3 (95% range 1.6–3.0). A 5-year backtest shows a typical error of ±15.7%, with 100% of held-out values landing inside the 95% band.19692029
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 →
20252.21.42.9
20262.21.52.9
20272.21.53.0
20282.31.53.0
20292.31.63.0

Black-headed Grosbeak Survey Routes in Idaho

Routes recording Black-headed Grosbeak 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 →
Cascade1119841974
Gifford920171971
Joel920241989
Rochat Divde820231993
Magic Mtn620241987
Featherville620241989
Picabo620212002
Naples520241978
Lolo Pass520191992
Challis520241976
Glenns Ferry519861986
Coolin520241986
Baldy Mountain520162013
Sawtooth City 2520232017
Pierce520051990
Mivoden420231977
Squirrel420241972
Nezperce320121996
Golden320151987
N Fork Cda R320181993
Centerville320191982
Mud Lake320142008
Cabarton320231985
Avery220231979
Springfield220171969

Black-headed Grosbeak Population Trend in Other States

alaskaarizonacaliforniacoloradokansasmontananebraskanevadanew-mexiconorth-dakotaoklahomaoregonsouth-dakotatexasutahwashingtonwyoming

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