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

Blue Grosbeak Population Trend in Colorado

All statesGeneralists

Blue Grosbeak in Colorado has risen sharply: up 74% on the route-weighted index since 1971.

+74%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 →
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 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 risen sharply in Colorado: up 73% 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 fall about 15% by 2029 — from 0.91 in 2024 to a central estimate of 0.77 (95% range 0.36–1.2). A 5-year backtest shows a typical error of ±31.1%, with 60% of held-out values landing inside the 95% band.

-15%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 →
0.77Projected 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 →
0.36–1.295% 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 →
±31.1%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 fall about 15% by 2029 — from 0.91 in 2024 to a central estimate of 0.77 (95% range 0.36–1.2). A 5-year backtest shows a typical error of ±31.1%, with 60% 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 →
20250.750.331.2
20260.750.341.2
20270.760.341.2
20280.770.351.2
20290.770.361.2

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
Trinchera1720221990
Waverly1520191988
Doyle Bridge 21520231998
Douglas Pass1320241985
Dolores919821968
Fort Morgan920241996
Cokedale720241996
Ninaview720241994
Haswell620241996
Baxter Pass520242000
Mica Butte419821974
De Beque420241993
Animas 2420212005
Pinneo320191984
Wray Gulch320211995
Adams Co.320212015
Campo320161998
Amherst320241996
Paonia320241992
Burlington320232003
Walsenburg320242003
Pritchett320241999
Abarr220231981
Boyero220171988

Blue Grosbeak Population Trend in Other States

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

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