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

Brewer's Sparrow In Sierra Nevada

All regionsSierra NevadaArid-land birds

Brewer's Sparrow in Sierra Nevada has declined: down 47% on the route-weighted index since 1971.

-47%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 →
14Routes 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 →

No notable trend signals for Brewer's Sparrow in Sierra Nevada. See the full index history below.

Brewer's Sparrow In Sierra Nevada Population Forecast

If the recent trend holds, Brewer's Sparrow in Sierra Nevada is projected to rise about 55% by 2030 — from 1.4 in 2025 to a central estimate of 2.2 (95% range 0.00–4.9). A 5-year backtest shows a typical error of ±150.2%, with 100% of held-out values landing inside the 95% band.

+55%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 →
2.2Projected 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 →
0.00–4.995% 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 →
±150.2%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, Brewer's Sparrow in Sierra Nevada is projected to rise about 55% by 2030 — from 1.4 in 2025 to a central estimate of 2.2 (95% range 0.00–4.9). A 5-year backtest shows a typical error of ±150.2%, with 100% of held-out values landing inside the 95% band.19692030
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 →
20262.20.004.9
20272.20.004.9
20282.20.004.9
20292.20.004.9
20302.20.004.9

Routes In Sierra Nevada

Routes recording Brewer's 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 →
SattleyCALIFORNIA142025
Last ChanceCALIFORNIA102019
Silver CityCALIFORNIA51977
GoumazCALIFORNIA42011
Little TruckeeCALIFORNIA42025
CrestviewCALIFORNIA42025
Eagle LakeCALIFORNIA32025
DardanelleCALIFORNIA32017
Hat CreekCALIFORNIA21992
Pine MountainCALIFORNIA22009
ChilcootCALIFORNIA22024
WestvilleCALIFORNIA11977
JohnsvilleCALIFORNIA12024
WoodfordsCALIFORNIA12024

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