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

Grasshopper Sparrow Population Trend in Colorado

All statesGrassland birds

Grasshopper Sparrow in Colorado has fallen sharply: down 58% on the route-weighted index since 1970.

-58%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 →
57YearsYears 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 58% 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 fall about 26% by 2030 — from 2.6 in 2025 to a central estimate of 1.9 (95% range 0.00–7.6). A 5-year backtest shows a typical error of ±51.5%, with 100% of held-out values landing inside the 95% band.

-26%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 →
1.9Projected 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 →
0.00–7.695% 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 →
±51.5%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 fall about 26% by 2030 — from 2.6 in 2025 to a central estimate of 1.9 (95% range 0.00–7.6). A 5-year backtest shows a typical error of ±51.5%, 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 →
20262.50.008.1
20272.30.008.0
20282.20.007.8
20292.00.007.7
20301.90.007.6

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 L4120251988
Kirk4120231992
Briggsdale3820251968
Waverly2720191988
Arsenal 22520252016
Last Chance2220151970
Pritchett2020251995
Rush1920251984
Neegrande1820251992
Abarr1720241968
Gilpin1720251970
Fleming1620251968
Two Buttes1620251973
Haswell1420241992
Pinneo1120251973
Sheridan Lak920161997
Cheyenne820251990
Nunn820251995
Adams Co.720211997
Edler720251992
Amherst620241992
Lamar520241973
Campo520251988
Burlington520232003
Limon520251996

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 2026-08-14.