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

Yellow-billed Magpie Population Trend in California

All statesGeneralists

Yellow-billed Magpie in California has declined: down 40% on the route-weighted index since 1970.

-40%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 →
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 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 22% by 2029 — from 1.6 in 2024 to a central estimate of 1.2 (95% range 0.00–3.2). A 5-year backtest shows a typical error of ±25.3%, with 100% of held-out values landing inside the 95% band.

-22%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 →
1.2Projected 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 →
0.00–3.295% 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 →
±25.3%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 22% by 2029 — from 1.6 in 2024 to a central estimate of 1.2 (95% range 0.00–3.2). A 5-year backtest shows a typical error of ±25.3%, 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 →
20251.50.003.5
20261.40.003.4
20271.40.003.3
20281.30.003.3
20291.20.003.2

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
Athlone2120041972
Jackson2019921972
Hughson1920241968
Coyote1620241972
Greenfield1520241973
Adelaida1420241970
Lockwood1320241972
Collegeville 21320232007
Tres Pinos1120031968
Westley1120241972
Zamora1120241972
Creston1020241972
Redding919831972
Cordova819811971
Oroville820241972
Ora Loma819951973
Rumsey620081969
Tomhead620111998
Oneals620051972
Staten Is.620241994
Carmel Val620241973
Yolla Bolly520231974

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