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

Black-billed Magpie Population Trend in Colorado

All statesGeneralists

Black-billed Magpie in Colorado has declined: down 48% on the route-weighted index since 1970.

-48%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 →
145Routes 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 ColoradoNotable 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 Colorado. See the full index history below.

Black-billed Magpie Population Forecast in Colorado

If the recent trend holds, Black-billed Magpie in Colorado is projected to fall about 40% by 2030 — from 7.9 in 2025 to a central estimate of 4.8 (95% range 0.00–10). A 5-year backtest shows a typical error of ±35%, with 100% of held-out values landing inside the 95% band.

-40%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 →
4.8Projected 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 →
0.00–1095% 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 →
±35%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 Colorado is projected to fall about 40% by 2030 — from 7.9 in 2025 to a central estimate of 4.8 (95% range 0.00–10). A 5-year backtest shows a typical error of ±35%, 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 →
20265.50.0011
20275.30.0011
20285.10.0011
20294.90.0010
20304.80.0010

Black-billed Magpie Survey Routes in Colorado

Routes recording Black-billed Magpie in Colorado.
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 →
Yampa11020231969
Yellowjacket Pass6620251998
Rifle Falls5420251998
Buford3720251970
Douglas Pass3620241982
Castleton3320251988
Elbert3320251998
Doyle Bridge3019971992
Aspen2720251979
Moffat2620251970
Blackhead Pk2520251991
Prospect Val2520001992
Powderhorn2520251995
Wilson Creek2320251990
Deadman Rd.2320251992
Dolores Riv2220251988
Moon Pass2220251998
De Beque2120251992
Parlin2020251968
Falfa2020251971
Doyle Bridge 22020251998
Dolores1919871968
Fox Creek1920251993
Arsenal1920151991
Doyleville1820251988

Black-billed Magpie Population Trend in Other States

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