BirdAnalyst
Species · Colorado · BBS 2026 Release · 1966–2025

Blue Grosbeak Population Trend in Colorado

All statesForest birds

Blue Grosbeak in Colorado has surged: up 76% on the route-weighted index since 1971.

+76%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 →
86Routes 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 Blue 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 →

Blue Grosbeak has surged in Colorado: up 76% on the route-weighted index since 1971.

Blue Grosbeak Population Forecast in Colorado

If the recent trend holds, Blue Grosbeak in Colorado is projected to stay roughly flat through 2030, near 0.78 (95% range 0.37–1.2). A 5-year backtest shows a typical error of ±22.1%, with 100% of held-out values landing inside the 95% band.

-0%Change by 2030TrendPercent 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 →
0.78Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.37–1.295% 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 →
±22.1%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, Blue Grosbeak in Colorado is projected to stay roughly flat through 2030, near 0.78 (95% range 0.37–1.2). A 5-year backtest shows a typical error of ±22.1%, with 100% of held-out values landing inside the 95% band.19682030
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 →
20260.760.341.2
20270.760.351.2
20280.770.361.2
20290.780.361.2
20300.780.371.2

Blue Grosbeak Survey Routes in Colorado

Routes recording Blue 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 →
Doyle Bridge2319971992
Waverly1520191988
Doyle Bridge 21520231998
Douglas Pass1320241985
Walsenburg1020252003
Dolores919821968
Cokedale720251996
Ninaview720241994
Pritchett720251999
Haswell620241996
Arsenal 2620252016
Gilpin520251974
Fort Morgan520251996
Baxter Pass520242000
Falfa420251971
Mica Butte419821974
Trinchera420251990
Neegrande420251992
Wray Gulch320211995
Wildhorse L320251999
Adams Co.320212015
Amherst320241996
De Beque320251993
Burlington320232003
Nucla320252008

Blue Grosbeak Population Trend in Other States

alabamaarizonaarkansascaliforniadelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamarylandminnesotamississippimissourimontananebraskanevadanew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvirginiawest-virginiawyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.