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

Brewer's Blackbird Population Trend in California

All statesGeneralists

Brewer's Blackbird in California has fallen sharply: down 68% on the route-weighted index since 1970.

-68%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 →
233Routes 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 Brewer's Blackbird 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 declinecomputed 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 →

Brewer's Blackbird has fallen sharply in California: down 67% on the route-weighted index since 1970.

Brewer's Blackbird Population Forecast in California

If the recent trend holds, Brewer's Blackbird in California is projected to fall about 37% by 2030 — from 25 in 2025 to a central estimate of 16 (95% range 0.00–32). A 5-year backtest shows a typical error of ±22.2%, 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 →
16Projected 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 →
0.00–3295% 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 →
±22.2%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, Brewer's Blackbird in California is projected to fall about 37% by 2030 — from 25 in 2025 to a central estimate of 16 (95% range 0.00–32). A 5-year backtest shows a typical error of ±22.2%, 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 →
2026193.336
2027182.435
2028181.434
2029170.4633
2030160.0032

Brewer's Blackbird Survey Routes in California

Routes recording Brewer's Blackbird 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 →
Dorris64620191972
Likely43020251971
Redding27919831972
Buena Vista20820191990
Parkfield20720251968
Oilfields19020131968
Collegeville 219020232007
Colma17519721968
Macdoel16020191972
Livermore14819911972
Ravendale14420251973
Caruthers12919871972
Gravesboro12519951968
Shafter12419891971
Hollister12020111973
Tres Pinos11920031968
Hollister 211820242012
Ingalls11620251973
Nubieber11520181970
Greenfield11020251973
Yreka11020191973
Athlone9820071972
Gazelle9520211988
Collegeville9320041968
South Lake8720062006

Brewer's Blackbird Population Trend in Other States

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