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

Fox Sparrow In Coastal California

All regionsCoastal CaliforniaGeneralists

Fox Sparrow in Coastal California has collapsed: down 83% on the route-weighted index since 1971.

-83%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 →
27Routes 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 →
54YearsYears 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 →

Fox Sparrow has collapsed in Coastal California: down 83% on the route-weighted index since 1971.

Fox Sparrow In Coastal California Population Forecast

If the recent trend holds, Fox Sparrow in Coastal California is projected to rise about 39% by 2028 — from 0.09 in 2023 to a central estimate of 0.12 (95% range 0.00–1.2). A 5-year backtest shows a typical error of ±93.3%, with 100% of held-out values landing inside the 95% band.

+39%Change by 2028TrendPercent 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 →
0.12Projected 2028 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–1.295% 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 →
±93.3%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, Fox Sparrow in Coastal California is projected to rise about 39% by 2028 — from 0.09 in 2023 to a central estimate of 0.12 (95% range 0.00–1.2). A 5-year backtest shows a typical error of ±93.3%, with 100% of held-out values landing inside the 95% band.19692028
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 →
20240.200.001.2
20250.180.001.2
20260.160.001.2
20270.140.001.2
20280.120.001.2

Routes In Coastal California

Routes recording Fox 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 →
ValyermoCALIFORNIA162019
Mt PinosCALIFORNIA82004
Lake HemetCALIFORNIA61986
Morro BayCALIFORNIA31974
Yolla BollyCALIFORNIA31973
Big BearCALIFORNIA21986
Green ValleyCALIFORNIA22023
Mt Pinos 2CALIFORNIA22021
TehamaCALIFORNIA21990
Cleveland NfCALIFORNIA22000
WoodlandsCALIFORNIA22023
Red BluffCALIFORNIA11986
Lake SuccessCALIFORNIA11978
CohassetCALIFORNIA12011
Sawmill MtnCALIFORNIA11974
TujungaCALIFORNIA11975
SisquocCALIFORNIA11987
Lockwood ValCALIFORNIA11988
Cp. PendletonCALIFORNIA11970
CrestonCALIFORNIA11999
White RiverCALIFORNIA11992
Gold HillCALIFORNIA11984
MoragaCALIFORNIA11988
Angelus OaksCALIFORNIA11993
Cal Hot SpgsCALIFORNIA12013

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