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

Yellow-billed Magpie Population Trend in California

All statesGeneralists

Yellow-billed Magpie in California has declined: down 35% on the route-weighted index since 1970.

-35%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 →
49Routes 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 Yellow-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 →

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

Yellow-billed Magpie Population Forecast in California

If the recent trend holds, Yellow-billed Magpie in California is projected to fall about 37% by 2030 — from 1.9 in 2025 to a central estimate of 1.2 (95% range 0.00–3.1). A 5-year backtest shows a typical error of ±19.3%, with 100% of held-out values landing inside the 95% band.

-37%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 →
1.2Projected 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 →
0.00–3.195% 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 →
±19.3%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, Yellow-billed Magpie in California is projected to fall about 37% by 2030 — from 1.9 in 2025 to a central estimate of 1.2 (95% range 0.00–3.1). A 5-year backtest shows a typical error of ±19.3%, 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 →
20261.50.003.4
20271.40.003.3
20281.30.003.3
20291.30.003.2
20301.20.003.1

Yellow-billed Magpie Survey Routes in California

Routes recording Yellow-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 →
Collegeville4620041968
Atwater4020041971
Tres Pinos 23620112005
Zamora3320251972
Greenfield2320251973
Athlone2120041972
Jackson2019921972
Adelaida2020251970
Glenn1720251971
Hughson1620251968
Westley1420251972
Collegeville 21320232007
Tres Pinos1120031968
Creston1020241972
Redding919831972
Lockwood920251972
Cohasset920251972
Cordova819811971
Ora Loma819951973
Carmel Val720251973
Rumsey620081969
Tomhead620111998
Oneals620051972
Staten Is.620251994
Yolla Bolly520231974

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