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Species · BCR 4 · BBS 2025 Release · 1966–2024

Willow Ptarmigan In BCR 4

All regionsBCR 4Generalists

Willow Ptarmigan in BCR 4 has fallen sharply: down 54% on the route-weighted index since 1984.

-54%Since 1984TrendPercent 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 RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
40YearsYears 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 →

Willow Ptarmigan has fallen sharply in BCR 4: down 54% on the route-weighted index since 1984.

Willow Ptarmigan In BCR 4 Population Forecast

If the recent trend holds, Willow Ptarmigan in BCR 4 is projected to fall about 66% by 2029 — from 0.47 in 2024 to a central estimate of 0.16 (95% range 0.00–0.78). A 5-year backtest shows a typical error of ±50.9%, with 100% of held-out values landing inside the 95% band.

-66%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 →
0.16Projected 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 →
0.00–0.7895% 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 →
±50.9%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, Willow Ptarmigan in BCR 4 is projected to fall about 66% by 2029 — from 0.47 in 2024 to a central estimate of 0.16 (95% range 0.00–0.78). A 5-year backtest shows a typical error of ±50.9%, with 100% of held-out values landing inside the 95% band.19822029
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 →
20250.200.000.82
20260.190.000.81
20270.180.000.80
20280.170.000.79
20290.160.000.78

Routes In BCR 4

Routes recording Willow Ptarmigan in BCR 4.
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 →
SavageALASKA122024
ToklatALASKA42024
Pinoche Tral (Short)ALASKA31984
MonahanALASKA22018
Caribou Mtn.ALASKA22023
EagleALASKA12022
MaclarenALASKA12024
CantwellALASKA12018
Hatcher PassALASKA12018
ColdfootALASKA12006
Donelly DomeALASKA12013
Paxson LakeALASKA11996
Nabesna RoadALASKA12016
Mccarthy Rd2ALASKA11991

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