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

Bell's Sparrow In Coastal California

All regionsCoastal CaliforniaGeneralists

Bell's Sparrow in Coastal California has declined: down 44% on the route-weighted index since 1971.

-44%Since 1971TrendPercent 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 →
51Routes 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 →
55YearsYears 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 Bell's Sparrow in Coastal California. See the full index history below.

Bell's Sparrow In Coastal California Population Forecast

If the recent trend holds, Bell's Sparrow in Coastal California is projected to rise about 68% by 2029 — from 0.49 in 2024 to a central estimate of 0.82 (95% range 0.02–1.6). A 5-year backtest shows a typical error of ±71%, with 100% of held-out values landing inside the 95% band.

+68%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 →
0.82Projected 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 →
0.02–1.695% 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 →
±71%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, Bell's Sparrow in Coastal California is projected to rise about 68% by 2029 — from 0.49 in 2024 to a central estimate of 0.82 (95% range 0.02–1.6). A 5-year backtest shows a typical error of ±71%, with 100% of held-out values landing inside the 95% band.19692029
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 →
20250.830.031.6
20260.830.021.6
20270.830.021.6
20280.820.021.6
20290.820.021.6

Routes In Coastal California

Routes recording Bell's Sparrow 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 →
StonyfordCALIFORNIA112018
Lockwood ValCALIFORNIA102019
RumseyCALIFORNIA82008
Hough SpringsCALIFORNIA82007
Cuyamaca PkCALIFORNIA72024
TujungaCALIFORNIA62012
Oak GroveCALIFORNIA52024
Bartlett SpsCALIFORNIA42018
GreenfieldCALIFORNIA42024
WoodlandsCALIFORNIA42021
PowayCALIFORNIA31980
MaricopaCALIFORNIA32024
VentucopaCALIFORNIA32001
Carrizo PlnCALIFORNIA32023
ShafterCALIFORNIA31985
San Benito Mtn.CALIFORNIA32009
Big BearCALIFORNIA21981
FairfaxCALIFORNIA21981
Elsinore MtnCALIFORNIA22010
Green ValleyCALIFORNIA22023
Lake CachumaCALIFORNIA22003
CrestonCALIFORNIA21996
Lake Hemet 2CALIFORNIA22013
Cleveland NfCALIFORNIA22014
Angelus OaksCALIFORNIA22004

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