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Species · California · BBS 2026 Release · 1966–2025

Black-billed Magpie Population Trend in California

All statesGeneralists

Black-billed Magpie in California has surged: up 109% on the route-weighted index since 1971.

+109%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 →
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 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 109% 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 160% by 2030 — from 0.55 in 2025 to a central estimate of 1.4 (95% range 0.46–2.4). A 5-year backtest shows a typical error of ±337.1%, with 0% of held-out values landing inside the 95% band.

+160%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 →
1.4Projected 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 →
0.46–2.495% 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 →
±337.1%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 160% by 2030 — from 0.55 in 2025 to a central estimate of 1.4 (95% range 0.46–2.4). A 5-year backtest shows a typical error of ±337.1%, with 0% of held-out values landing inside the 95% band.19692030
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 →
20261.40.432.4
20271.40.442.4
20281.40.442.4
20291.40.452.4
20301.40.462.4

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
Gazelle1320211988
Davis Creek1120251972
Cedarville1020251974
Iron Gate720191988
Likely720251971
Ingalls720251973
Clear Lk Res620181972
Sattley520251972
Yreka520191973
Paxton420241998
Dorris420191972
Crowley Lake320221977
Madeline320251997
Mt Shasta320191972
Bodie320251982
Nubieber220171970
Dardanelle220141973
Big Pine219811969
Bridgeport219761972
Genesee220241974
Tionesta120061997
Crowder Flat120192013
Haiwee Res119921992
Honey Lake120251972

Black-billed Magpie Population Trend in Other States

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