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

Brewer's Blackbird Population Trend in California

All statesGeneralists

Brewer's Blackbird in California has fallen sharply: down 70% on the route-weighted index since 1970.

-70%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 →
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 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 70% 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 42% by 2029 — from 28 in 2024 to a central estimate of 16 (95% range 0.00–32). A 5-year backtest shows a typical error of ±22.5%, with 100% 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 →
16Projected 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 →
0.00–3295% 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 →
±22.5%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 42% by 2029 — from 28 in 2024 to a central estimate of 16 (95% range 0.00–32). A 5-year backtest shows a typical error of ±22.5%, 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 →
2025203.836
2026192.935
2027181.934
2028170.9633
2029160.0032

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
Likely50720241971
Cedarville32820241974
Redding27919831972
Buena Vista20820191990
Oilfields19020131968
Collegeville 219020232007
Glenn18520231971
Colma17519721968
Macdoel16020191972
Livermore14819911972
Sattley14320241972
Caruthers12919871972
Gravesboro12519951968
Shafter12419891971
Parkfield12120241968
Hollister12020111973
Tres Pinos11920031968
Hollister 211820242012
Greenfield11620241973
Nubieber11520181970
Yreka11020191973
Athlone9820071972
Crowley Lake9720241972
Gazelle9520211988

Brewer's Blackbird Population Trend in Other States

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