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

Black-throated Sparrow In Coastal California

All regionsCoastal CaliforniaArid-land birds

Black-throated Sparrow in Coastal California has collapsed: down 83% on the route-weighted index since 1972.

-83%Since 1972TrendPercent 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 →
17Routes 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 →
51YearsYears 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 →

Black-throated Sparrow has collapsed in Coastal California: down 82% on the route-weighted index since 1972.

Black-throated Sparrow In Coastal California Population Forecast

If the recent trend holds, Black-throated Sparrow in Coastal California is projected to stay roughly flat through 2029, near 0.07 (95% range 0.00–0.42). A 5-year backtest shows a typical error of ±57.8%, with 100% of held-out values landing inside the 95% band.

+2%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 →
0.07Projected 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 →
0.00–0.4295% 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 →
±57.8%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, Black-throated Sparrow in Coastal California is projected to stay roughly flat through 2029, near 0.07 (95% range 0.00–0.42). A 5-year backtest shows a typical error of ±57.8%, with 100% of held-out values landing inside the 95% band.19702029
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 →
20250.080.000.43
20260.080.000.43
20270.070.000.43
20280.070.000.42
20290.070.000.42

Routes In Coastal California

Routes recording Black-throated 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 →
Mt PinosCALIFORNIA71997
Green ValleyCALIFORNIA42023
Big BearCALIFORNIA31986
Cuyamaca PkCALIFORNIA31976
VentucopaCALIFORNIA31995
FolsomCALIFORNIA22012
FallsvaleCALIFORNIA21975
Mt LagunaCALIFORNIA21975
AnzaCALIFORNIA22003
JacumbaCALIFORNIA22024
Oak GroveCALIFORNIA12022
TujungaCALIFORNIA11970
Mesa GrandeCALIFORNIA12019
Carrizo PlnCALIFORNIA11977
CopperopolisCALIFORNIA12015
Lake Hemet 2CALIFORNIA11993
WoodlandsCALIFORNIA12024

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