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

Cassin's Sparrow Population Trend in Colorado

All statesGrassland birds

Cassin's Sparrow in Colorado has surged: up 215% on the route-weighted index since 1970.

+215%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 →
59Routes 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 Cassin's 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 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 →

Cassin's Sparrow has surged in Colorado: up 215% on the route-weighted index since 1970.

Cassin's Sparrow Population Forecast in Colorado

If the recent trend holds, Cassin's Sparrow in Colorado is projected to fall about 24% by 2029 — from 8.2 in 2024 to a central estimate of 6.2 (95% range 0.00–21). A 5-year backtest shows a typical error of ±44.1%, with 100% of held-out values landing inside the 95% band.

-24%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 →
6.2Projected 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 →
0.00–2195% 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 →
±44.1%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, Cassin's Sparrow in Colorado is projected to fall about 24% by 2029 — from 8.2 in 2024 to a central estimate of 6.2 (95% range 0.00–21). A 5-year backtest shows a typical error of ±44.1%, 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 →
20256.80.0021
20266.60.0021
20276.50.0021
20286.40.0021
20296.20.0021

Cassin's Sparrow Survey Routes in Colorado

Routes recording Cassin's 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 →
Crowley11120241989
Pritchett10220241995
Boyero8720171979
Campo8320191988
Timpas7420191995
Gilpin7020241970
Edison6520241988
Ellicott5720241994
Neegrande4620241992
Rush4420241983
Villegreen3720241988
Rockport3420241996
Abarr2920241970
Haswell2920241992
Ninaview2920241994
Kirk2720231992
Trinchera2420221990
Pinneo2320191973
Lamar2020241973
Edler2020241992
Cone Mtn2020241988
Cheyenne1920241990
Karval1820191995
Arsenal 21720242017
Two Buttes1720151973

Cassin's Sparrow Population Trend in Other States

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