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

Grasshopper Sparrow Population Trend in Colorado

All statesGrassland birds

Grasshopper Sparrow in Colorado has fallen sharply: down 63% on the route-weighted index since 1970.

-63%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 →
66Routes 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 Grasshopper Sparrow 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 declinecomputed 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 →

Grasshopper Sparrow has fallen sharply in Colorado: down 63% on the route-weighted index since 1970.

Grasshopper Sparrow Population Forecast in Colorado

If the recent trend holds, Grasshopper Sparrow in Colorado is projected to stay roughly flat through 2029, near 2.0 (95% range 0.00–7.8). A 5-year backtest shows a typical error of ±49.6%, with 100% of held-out values landing inside the 95% band.

+6%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 →
2.0Projected 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 →
0.00–7.895% 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 →
±49.6%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, Grasshopper Sparrow in Colorado is projected to stay roughly flat through 2029, near 2.0 (95% range 0.00–7.8). A 5-year backtest shows a typical error of ±49.6%, 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 →
20252.60.008.3
20262.50.008.2
20272.30.008.0
20282.20.007.9
20292.00.007.8

Grasshopper Sparrow Survey Routes in Colorado

Routes recording Grasshopper Sparrow 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 →
Wildhorse L5520241988
Kirk4120231992
Stoneham2920211992
Waverly2720191988
Pinneo2620191973
Campo2520191988
Last Chance2220151970
Nunn1920211995
Abarr1720241968
Rush1520241984
Haswell1420241992
Limon1220241996
Briggsdale1020241968
Neegrande1020241992
Gilpin920241970
Sheridan Lak920161997
Pritchett820241995
Adams Co.720211997
Amherst620241992
Lamar520241973
Two Buttes520151973
Cheyenne520241990
Burlington520232003
Fleming420241968
Arsenal 2420242016

Grasshopper Sparrow Population Trend in Other States

alabamaarizonaarkansascaliforniaconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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