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

Curve-billed Thrasher Population Trend in Colorado

All statesArid-land birds

Curve-billed Thrasher in Colorado has increased: up 46% on the route-weighted index since 1981.

+46%Since 1981TrendPercent 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 →
14Routes 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 →
34YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Curve-billed Thrasher 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 →

No notable trend signals for Curve-billed Thrasher in Colorado. See the full index history below.

Curve-billed Thrasher Population Forecast in Colorado

If the recent trend holds, Curve-billed Thrasher in Colorado is projected to fall about 44% by 2029 — from 0.08 in 2024 to a central estimate of 0.05 (95% range 0.01–0.09). A 5-year backtest shows a typical error of ±49.8%, with 80% of held-out values landing inside the 95% band.

-44%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 →
0.05Projected 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 →
0.01–0.0995% 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 →
±49.8%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, Curve-billed Thrasher in Colorado is projected to fall about 44% by 2029 — from 0.08 in 2024 to a central estimate of 0.05 (95% range 0.01–0.09). A 5-year backtest shows a typical error of ±49.8%, with 80% of held-out values landing inside the 95% band.19732029
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 →
20250.040.000.09
20260.040.000.09
20270.050.000.09
20280.050.010.09
20290.050.010.09

Curve-billed Thrasher Survey Routes in Colorado

Routes recording Curve-billed Thrasher 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 →
Villegreen320241989
Crowley220241990
Gribbles Prk120242024
Sheridan Lak120062006
Ninaview120152006
Campo120181998
Doyle Bridge 2120182018
Timpas120192004
Parlin120022002
Mica Butte119811973
Gilpin120241993
Neegrande120122002
Cone Mtn120241989
Ellicott120192006

Curve-billed Thrasher Population Trend in Other States

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