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

Brown-headed Cowbird In Coastal California

All regionsCoastal CaliforniaGeneralists

Brown-headed Cowbird in Coastal California has increased: up 49% on the route-weighted index since 1970.

+49%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 →
116Routes 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 →

No notable trend signals for Brown-headed Cowbird in Coastal California. See the full index history below.

Brown-headed Cowbird In Coastal California Population Forecast

If the recent trend holds, Brown-headed Cowbird in Coastal California is projected to rise about 54% by 2029 — from 5.7 in 2024 to a central estimate of 8.8 (95% range 3.5–14). A 5-year backtest shows a typical error of ±108.8%, with 60% of held-out values landing inside the 95% band.

+54%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 →
8.8Projected 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 →
3.5–1495% 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 →
±108.8%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, Brown-headed Cowbird in Coastal California is projected to rise about 54% by 2029 — from 5.7 in 2024 to a central estimate of 8.8 (95% range 3.5–14). A 5-year backtest shows a typical error of ±108.8%, 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 →
20258.73.414
20268.73.414
20278.83.414
20288.83.514
20298.83.514

Routes In Coastal California

Routes recording Brown-headed Cowbird 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 →
TiptonCALIFORNIA491997
AtwaterCALIFORNIA332012
CaruthersCALIFORNIA311987
JacksonCALIFORNIA301992
CordovaCALIFORNIA281980
Staten Is.CALIFORNIA282024
Ora LomaCALIFORNIA272024
Red BluffCALIFORNIA232024
GlennCALIFORNIA212023
CollegevilleCALIFORNIA202004
HollisterCALIFORNIA202011
CoyoteCALIFORNIA202024
Big BearCALIFORNIA191986
Yokohl ValCALIFORNIA181997
Collegeville 2CALIFORNIA182023
PenningtonCALIFORNIA172024
White RiverCALIFORNIA171992
TracyCALIFORNIA172009
AthloneCALIFORNIA162007
CopperopolisCALIFORNIA152024
BakersfieldCALIFORNIA142023
VentucopaCALIFORNIA141998
HughsonCALIFORNIA132024
OilfieldsCALIFORNIA102005
Orange CoveCALIFORNIA102016

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