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

Black-billed Magpie Population Trend in Colorado

All statesGeneralists

Black-billed Magpie in Colorado has declined: down 46% on the route-weighted index since 1970.

-46%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 →
144Routes 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 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 35% by 2029 — from 7.3 in 2024 to a central estimate of 4.8 (95% range 0.00–10). A 5-year backtest shows a typical error of ±29.6%, with 100% of held-out values landing inside the 95% band.

-35%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 →
4.8Projected 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 →
0.00–1095% 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 →
±29.6%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 35% by 2029 — from 7.3 in 2024 to a central estimate of 4.8 (95% range 0.00–10). A 5-year backtest shows a typical error of ±29.6%, 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 →
20255.60.0011
20265.40.0011
20275.20.0011
20285.00.0011
20294.80.0010

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
Buford4520241970
Castleton4320241988
Yellowjacket Pass4120241998
Aspen3920241979
Douglas Pass3620241982
Deadman Rd.3220241992
De Beque3120241992
Doyle Bridge3019971992
Prospect Val2520001992
Elbert2520241998
Wilson Creek2420241990
Rifle Falls2320211998
Paonia2220241992
Powderhorn2220231995
Moffat2120241970
Mcphee Res.2020241996
Dolores1919871968
Fox Creek1920241993
Arsenal1920151991
Radium1820131998
Moon Pass1820241998
Cortez 21820172009
Falfa1720241971
Pagosa Spgs1719821968

Black-billed Magpie Population Trend in Other States

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