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Species · Montana · BBS 2026 Release · 1966–2025

Chestnut-collared Longspur Population Trend in Montana

All statesGrassland birds

Chestnut-collared Longspur in Montana has surged: up 76% on the route-weighted index since 1970.

+76%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 →
45Routes 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 Chestnut-collared Longspur Trends in MontanaNotable 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 →

Chestnut-collared Longspur has surged in Montana: up 76% on the route-weighted index since 1970.

Chestnut-collared Longspur Population Forecast in Montana

If the recent trend holds, Chestnut-collared Longspur in Montana is projected to fall about 32% by 2030 — from 7.2 in 2025 to a central estimate of 4.9 (95% range 0.00–11). A 5-year backtest shows a typical error of ±42.8%, with 100% of held-out values landing inside the 95% band.

-32%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 →
4.9Projected 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 →
0.00–1195% 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 →
±42.8%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, Chestnut-collared Longspur in Montana is projected to fall about 32% by 2030 — from 7.2 in 2025 to a central estimate of 4.9 (95% range 0.00–11). A 5-year backtest shows a typical error of ±42.8%, 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 →
20265.00.0011
20275.00.0011
20285.00.0011
20294.90.0011
20304.90.0011

Chestnut-collared Longspur Survey Routes in Montana

Routes recording Chestnut-collared Longspur in Montana.
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 →
Coleman Coulee9520242017
Roundup7720252016
Dinosaurs H.M.7420252018
Oswego7120251978
Ester Lake5620252015
Glentana5220252015
Chinook4220252015
Saco3820252015
Albion3720251982
Webster3120251978
Virgelle2920251979
Westby2320252016
Shelby1920252015
Circle1620231969
Harlem1520211968
Glasgow1420241968
Jordan South1320252016
Redstone1220251968
Wheat Basin920252017
Flatwillow820061971
Lambert720252021
Whitlash420242009
Augusta320101976
Great Falls320171972
Jordan320181982

Chestnut-collared Longspur Population Trend in Other States

coloradominnesotanebraskanorth-dakotasouth-dakotawyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.