BirdAnalyst
Species · BCR 15 · BBS 2026 Release · 1966–2025

Fox Sparrow In Sierra Nevada

All regionsSierra NevadaForest birds

Fox Sparrow in Sierra Nevada has surged: up 166% on the route-weighted index since 1970.

+166%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 →
38Routes 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 →
57YearsYears 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 increasecomputed 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 surged in Sierra Nevada: up 166% on the route-weighted index since 1970.

Fox Sparrow In Sierra Nevada Population Forecast

If the recent trend holds, Fox Sparrow in Sierra Nevada is projected to rise about 35% by 2030 — from 8.3 in 2025 to a central estimate of 11 (95% range 2.8–20). A 5-year backtest shows a typical error of ±24.9%, with 100% of held-out values landing inside the 95% band.

+35%Change by 2030TrendPercent 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 →
11Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
2.8–2095% 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 →
±24.9%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 Sierra Nevada is projected to rise about 35% by 2030 — from 8.3 in 2025 to a central estimate of 11 (95% range 2.8–20). A 5-year backtest shows a typical error of ±24.9%, with 100% of held-out values landing inside the 95% band.19682030
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 →
2026112.920
2027112.920
2028112.820
2029112.820
2030112.820

Routes In Sierra Nevada

Routes recording Fox Sparrow in Sierra Nevada.
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 →
Tahoe NfCALIFORNIA401994
WestvilleCALIFORNIA342025
Greenhorn MtCALIFORNIA322008
GeneseeCALIFORNIA292024
Pine MountainCALIFORNIA252017
JohnsvilleCALIFORNIA232025
Cottage SpgsCALIFORNIA201975
LakeshoreCALIFORNIA202024
Pollock PinesCALIFORNIA202025
Tuolumne GroveCALIFORNIA192025
RivertonCALIFORNIA182025
ChesterCALIFORNIA132017
Meadow ValleyCALIFORNIA122025
DardanelleCALIFORNIA112019
Lassen ParkCALIFORNIA81989
Hat CreekCALIFORNIA82018
Little TruckeeCALIFORNIA82025
Butte MeadowCALIFORNIA72014
DownievilleCALIFORNIA72025
CoultervilleCALIFORNIA62019
Last ChanceCALIFORNIA62019
Chaos CraterCALIFORNIA52019
Silver CityCALIFORNIA42013
LumberyardCALIFORNIA32025
WoodfordsCALIFORNIA22025

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.