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

Black-billed Magpie Population Trend in California

All statesGeneralists

Black-billed Magpie in California has surged: up 101% on the route-weighted index since 1971.

+101%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 →
31Routes 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 →
55YearsYears 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 CaliforniaNotable 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 increasecomputed 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 →

Black-billed Magpie has surged in California: up 101% on the route-weighted index since 1971.

Black-billed Magpie Population Forecast in California

If the recent trend holds, Black-billed Magpie in California is projected to rise about 94% by 2029 — from 0.77 in 2024 to a central estimate of 1.5 (95% range 0.54–2.5). A 5-year backtest shows a typical error of ±290.2%, with 20% of held-out values landing inside the 95% band.

+94%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 →
1.5Projected 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 →
0.54–2.595% 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 →
±290.2%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 California is projected to rise about 94% by 2029 — from 0.77 in 2024 to a central estimate of 1.5 (95% range 0.54–2.5). A 5-year backtest shows a typical error of ±290.2%, with 20% of held-out values landing inside the 95% band.19692029
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 →
20251.50.512.4
20261.50.522.4
20271.50.532.5
20281.50.542.5
20291.50.542.5

Black-billed Magpie Survey Routes in California

Routes recording Black-billed Magpie in California.
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 →
Macdoel3520191972
Cedarville2420241974
Davis Creek1920241972
Ingalls1720011973
Gazelle1320211988
Likely920241971
Iron Gate720191988
Honey Lake620241972
Clear Lk Res620181972
Yreka520191973
Paxton420241998
Dorris420191972
Crowley Lake320221977
Madeline320241997
Mt Shasta320191972
Nubieber220171970
Dardanelle220141973
Big Pine219811969
Sattley220241972
Bridgeport219761972
Genesee220241974
Bodie220241982
Tionesta120061997
Crowder Flat120192013
Haiwee Res119921992

Black-billed Magpie Population Trend in Other States

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