BirdAnalyst
Species · BCR 10 · BBS 2025 Release · 1966–2024

Chestnut-collared Longspur In Northern Rockies

All regionsNorthern RockiesGeneralists

Chestnut-collared Longspur in Northern Rockies has collapsed: down 87% on the route-weighted index since 1971.

-87%Since 1971TrendPercent 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 →
8Routes In RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
38YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable 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 Northern Rockies: down 87% on the route-weighted index since 1971.

Chestnut-collared Longspur In Northern Rockies Population Forecast

If the recent trend holds, Chestnut-collared Longspur in Northern Rockies is projected to stay roughly flat through 2027, near 0.00 (95% range 0.00–0.20). A 5-year backtest shows a typical error of ±104.4%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2027TrendPercent 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 2027 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.2095% 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 →
±104.4%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 Northern Rockies is projected to stay roughly flat through 2027, near 0.00 (95% range 0.00–0.20). A 5-year backtest shows a typical error of ±104.4%, with 100% of held-out values landing inside the 95% band.19692027
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 →
20230.000.000.20
20240.000.000.20
20250.000.000.20
20260.000.000.20
20270.000.000.20

Routes In Northern Rockies

Routes recording Chestnut-collared Longspur in Northern Rockies.
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 →
AugustaMONTANA32010
RawlinsWYOMING32005
St MaryMONTANA21980
Rock RiverWYOMING22022
Twin BridgesMONTANA11976
ClarkWYOMING12011
EtheteWYOMING11992
BaggsWYOMING11995

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