BirdAnalyst
Species · BCR 15 · BBS 2025 Release · 1966–2024

Fox Sparrow In Sierra Nevada

All regionsSierra NevadaGeneralists

Fox Sparrow in Sierra Nevada has surged: up 191% on the route-weighted index since 1970.

+191%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 →
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 →

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 191% 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 23% by 2029 — from 9.4 in 2024 to a central estimate of 12 (95% range 3.0–20). A 5-year backtest shows a typical error of ±29.3%, with 100% of held-out values landing inside the 95% band.

+23%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 →
12Projected 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 →
3.0–2095% 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 →
±29.3%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 Sierra Nevada is projected to rise about 23% by 2029 — from 9.4 in 2024 to a central estimate of 12 (95% range 3.0–20). A 5-year backtest shows a typical error of ±29.3%, with 100% 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 →
2025123.120
2026123.120
2027123.120
2028123.120
2029123.020

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 →
WestvilleCALIFORNIA482024
Tahoe NfCALIFORNIA401994
Greenhorn MtCALIFORNIA322008
JohnsvilleCALIFORNIA292024
GeneseeCALIFORNIA292024
Pine MountainCALIFORNIA252017
Cottage SpgsCALIFORNIA201975
LakeshoreCALIFORNIA202024
Tuolumne GroveCALIFORNIA152024
ChesterCALIFORNIA132017
Meadow ValleyCALIFORNIA122024
Little TruckeeCALIFORNIA122023
DardanelleCALIFORNIA112019
Lassen ParkCALIFORNIA81989
Hat CreekCALIFORNIA82018
LumberyardCALIFORNIA72024
Butte MeadowCALIFORNIA72014
Pollock PinesCALIFORNIA72024
DownievilleCALIFORNIA62024
CoultervilleCALIFORNIA62019
Last ChanceCALIFORNIA62019
Chaos CraterCALIFORNIA52019
Silver CityCALIFORNIA42013
RivertonCALIFORNIA42023
WoodfordsCALIFORNIA22024

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