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

Black-headed Grosbeak Population Trend in Colorado

All statesGeneralists

Black-headed Grosbeak in Colorado has surged: up 216% on the route-weighted index since 1970.

+216%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 →
113Routes 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 Black-headed Grosbeak 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 →

Black-headed Grosbeak has surged in Colorado: up 216% on the route-weighted index since 1970.

Black-headed Grosbeak Population Forecast in Colorado

If the recent trend holds, Black-headed Grosbeak in Colorado is projected to stay roughly flat through 2029, near 2.8 (95% range 1.9–3.7). A 5-year backtest shows a typical error of ±11.7%, with 100% of held-out values landing inside the 95% band.

-5%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 →
2.8Projected 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 →
1.9–3.795% 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 →
±11.7%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 Colorado is projected to stay roughly flat through 2029, near 2.8 (95% range 1.9–3.7). A 5-year backtest shows a typical error of ±11.7%, 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 →
20252.61.73.5
20262.61.73.5
20272.71.83.6
20282.71.83.6
20292.81.93.7

Black-headed Grosbeak Survey Routes in Colorado

Routes recording Black-headed Grosbeak 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 →
Mesaverde Np3920241996
Cokedale3120241995
Walsenburg2920241994
Animas2120041996
Mcphee Res.1920241996
Paonia1320241992
Nucla1320241999
Douglas Pass1220241985
Wilson Creek1220241990
Baxter Pass1220241996
Blackhead Pk1020211991
Wet Mtns.920241993
Uncompahgre720241988
Ludlow720161998
Cortez620081988
Fox Creek620241993
Gold Hill620121998
Elbert620221998
Yampa520231987
Dolores Riv520241988
Deadman Rd.520241992
Thomasville520181993
Comanche Pk520241995
Westcliffe520241998
Pagosa Spgs419821968

Black-headed Grosbeak Population Trend in Other States

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