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

Chestnut-collared Longspur Population Trend in Colorado

All statesGeneralists

Chestnut-collared Longspur in Colorado has collapsed: down 95% on the route-weighted index since 1977.

-95%Since 1977TrendPercent 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 →
12Routes 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 →
39YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Chestnut-collared Longspur 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 →

Chestnut-collared Longspur has collapsed in Colorado: down 95% on the route-weighted index since 1977.

Chestnut-collared Longspur Population Forecast in Colorado

If the recent trend holds, Chestnut-collared Longspur in Colorado is projected to fall about 100% by 2029 — from 0.07 in 2024 to a central estimate of 0.00 (95% range 0.00–0.49). A 5-year backtest shows a typical error of ±486%, with 100% of held-out values landing inside the 95% band.

-100%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 →
0.00Projected 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 →
0.00–0.4995% 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 →
±486%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, Chestnut-collared Longspur in Colorado is projected to fall about 100% by 2029 — from 0.07 in 2024 to a central estimate of 0.00 (95% range 0.00–0.49). A 5-year backtest shows a typical error of ±486%, with 100% 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 →
20250.000.000.49
20260.000.000.49
20270.000.000.49
20280.000.000.49
20290.000.000.49

Chestnut-collared Longspur Survey Routes in Colorado

Routes recording Chestnut-collared Longspur 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 →
Pinneo620161973
Nunn620211995
Briggsdale520081973
Rockport320241994
Adams Co.320162016
Gordon Creek320051988
Limon320242016
Pritchett120192019
Grover120241992
Boyero119951995
Gilpin120172017
Cone Mtn119921992

Chestnut-collared Longspur Population Trend in Other States

minnesotamontananebraskanorth-dakotasouth-dakotawyoming

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