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

Black-headed Grosbeak Population Trend in California

All statesGeneralists

Black-headed Grosbeak in California has held roughly steady: down 8% on the route-weighted index since 1970.

-8%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 →
232Routes 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-headed Grosbeak 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 Black-headed Grosbeak in California. See the full index history below.

Black-headed Grosbeak Population Forecast in California

If the recent trend holds, Black-headed Grosbeak in California is projected to rise about 42% by 2029 — from 6.5 in 2024 to a central estimate of 9.2 (95% range 6.5–12). A 5-year backtest shows a typical error of ±36.4%, with 60% of held-out values landing inside the 95% band.

+42%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 →
9.2Projected 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 →
6.5–1295% 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 →
±36.4%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-headed Grosbeak in California is projected to rise about 42% by 2029 — from 6.5 in 2024 to a central estimate of 9.2 (95% range 6.5–12). A 5-year backtest shows a typical error of ±36.4%, with 60% 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 →
20259.26.512
20269.26.512
20279.26.512
20289.26.512
20299.26.512

Black-headed Grosbeak Survey Routes in California

Routes recording Black-headed Grosbeak 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 →
Mt Baldy6920241970
Horse Creek6720191970
Placerville5920241997
Forest Hill5020221997
White River4919921972
Forest Hill 23720052005
Lake Success3319961972
Bartlett Sps3320181972
Cuyamaca Pk3220241970
Cecilville3220171999
Cal Hot Spgs3120191993
Burnt Ranch3020161998
Longvale2920231972
Stonyford2920182015
Greenhorn Mt2820081971
Cohasset2720241972
Downieville2720241975
South Fork Mtn2620222000
Hullville2520191968
Jackson2519921972
Orleans2520121972
Silver City2420131974
Elsinore Mtn2320241970
Iron Gate2320191988
Lonesome Rdg2320141994

Black-headed Grosbeak Population Trend in Other States

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