BirdAnalyst
Species · Montana · BBS 2026 Release · 1966–2025

Black-billed Magpie Population Trend in Montana

All statesGeneralists

Black-billed Magpie in Montana has declined: down 30% on the route-weighted index since 1970.

-30%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 →
94Routes 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 Black-billed Magpie 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 →

No notable trend signals for Black-billed Magpie in Montana. See the full index history below.

Black-billed Magpie Population Forecast in Montana

If the recent trend holds, Black-billed Magpie in Montana is projected to fall about 21% by 2030 — from 9.0 in 2025 to a central estimate of 7.1 (95% range 1.9–12). A 5-year backtest shows a typical error of ±21.8%, with 100% of held-out values landing inside the 95% band.

-21%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 →
7.1Projected 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 →
1.9–1295% 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 →
±21.8%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, Black-billed Magpie in Montana is projected to fall about 21% by 2030 — from 9.0 in 2025 to a central estimate of 7.1 (95% range 1.9–12). A 5-year backtest shows a typical error of ±21.8%, 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 →
20267.22.012
20277.22.012
20287.21.912
20297.11.912
20307.11.912

Black-billed Magpie Survey Routes in Montana

Routes recording Black-billed Magpie 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 →
Clyde Park7020252018
Chestnut6920251968
Willow Creek 24920251982
Heart Butte3920252015
Glen3520251977
Victor2820251993
Polson2620251972
Church Hill2520252017
Cramer Creek2520162008
Willow Creek2419811972
Pablo Res.2420251995
Kalispell2220251968
Beaverhead2220251973
St. Mary 22220252009
Fort Logan2220252018
Freeman Creek2120162015
East Glacier Park2020252015
St Mary1820081968
Highwood1820251968
Twin Bridges1819761968
Reed Point1820251977
Brandenberg1820251968
Chuffey Spring1820252016
Muddy Creek1620152015
Redstone1520251968

Black-billed Magpie Population Trend in Other States

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