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

Chestnut-collared Longspur Population Trend in Montana

All statesGeneralists

Chestnut-collared Longspur in Montana has risen sharply: up 66% on the route-weighted index since 1970.

+66%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 →
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 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 risen sharply in Montana: up 66% 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 38% by 2029 — from 7.6 in 2024 to a central estimate of 4.7 (95% range 0.00–11). A 5-year backtest shows a typical error of ±41.1%, with 100% of held-out values landing inside the 95% band.

-38%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 →
4.7Projected 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 →
0.00–1195% 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 →
±41.1%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, Chestnut-collared Longspur in Montana is projected to fall about 38% by 2029 — from 7.6 in 2024 to a central estimate of 4.7 (95% range 0.00–11). A 5-year backtest shows a typical error of ±41.1%, 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 →
20254.90.0011
20264.80.0011
20274.80.0011
20284.70.0011
20294.70.0011

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 →
Dinosaurs H.M.12320242018
Oswego7720241978
Roundup7120242016
Coleman Coulee6820232017
Glentana5820242015
Ester Lake4320242015
Chinook4220242015
Virgelle3520241979
Albion3420241982
Webster2920241978
Saco2420242015
Shelby2320242015
Circle1620231969
Harlem1520211968
Glasgow1420241968
Lambert1320242021
Westby1220242016
Flatwillow820061971
Jordan South820242016
Wheat Basin820242017
Maynard Coulee620242017
Redstone520241968
Shawmut420241979
Gildford420242015
Whitlash420242009

Chestnut-collared Longspur Population Trend in Other States

coloradominnesotanebraskanorth-dakotasouth-dakotawyoming

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