BirdAnalyst
Species · BCR 32 · BBS 2025 Release · 1966–2024

Brewer's Blackbird In Coastal California

All regionsCoastal CaliforniaGeneralists

Brewer's Blackbird in Coastal California has collapsed: down 77% on the route-weighted index since 1970.

-77%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 →
118Routes In RegionSurvey 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 SignalsNotable 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 collapsed in Coastal California: down 77% on the route-weighted index since 1970.

Brewer's Blackbird In Coastal California Population Forecast

If the recent trend holds, Brewer's Blackbird in Coastal California is projected to fall about 34% by 2029 — from 25 in 2024 to a central estimate of 17 (95% range 0.00–48). A 5-year backtest shows a typical error of ±10.5%, with 100% of held-out values landing inside the 95% band.

-34%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 →
17Projected 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 →
0.00–4895% 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 →
±10.5%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 Coastal California is projected to fall about 34% by 2029 — from 25 in 2024 to a central estimate of 17 (95% range 0.00–48). A 5-year backtest shows a typical error of ±10.5%, 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 →
2025230.0054
2026220.0053
2027200.0051
2028180.0049
2029170.0048

Routes In Coastal California

Routes recording Brewer's Blackbird in Coastal 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 →
ReddingCALIFORNIA2791983
Buena VistaCALIFORNIA2082019
OilfieldsCALIFORNIA1902013
Collegeville 2CALIFORNIA1902023
GlennCALIFORNIA1852023
ColmaCALIFORNIA1751972
LivermoreCALIFORNIA1481991
CaruthersCALIFORNIA1291987
GravesboroCALIFORNIA1251995
ShafterCALIFORNIA1241989
ParkfieldCALIFORNIA1212024
HollisterCALIFORNIA1202011
Tres PinosCALIFORNIA1192003
Hollister 2CALIFORNIA1182024
GreenfieldCALIFORNIA1162024
AthloneCALIFORNIA982007
CollegevilleCALIFORNIA932004
South LakeCALIFORNIA872006
WestleyCALIFORNIA832024
Tres Pinos 2CALIFORNIA782011
RiovistaCALIFORNIA762024
TiptonCALIFORNIA741997
CordovaCALIFORNIA731981
OrlandCALIFORNIA682022
Big BearCALIFORNIA671986

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