BirdAnalyst
Species · BCR 5 · BBS 2025 Release · 1966–2024

Brewer's Sparrow In Northern Pacific Rainforest

All regionsNorthern Pacific RainforestGeneralists

Brewer's Sparrow in Northern Pacific Rainforest has fallen sharply: down 60% on the route-weighted index since 1978.

-60%Since 1978TrendPercent 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 →
3Routes 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 →
34YearsYears 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 →

Brewer's Sparrow has fallen sharply in Northern Pacific Rainforest: down 60% on the route-weighted index since 1978.

Brewer's Sparrow In Northern Pacific Rainforest Population Forecast

If the recent trend holds, Brewer's Sparrow in Northern Pacific Rainforest is projected to fall about 57% by 2024 — from 0.05 in 2019 to a central estimate of 0.02 (95% range 0.00–0.17). A 5-year backtest shows a typical error of ±57%, with 100% of held-out values landing inside the 95% band.

-57%Change by 2024TrendPercent 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 →
0.02Projected 2024 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.1795% 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%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 Northern Pacific Rainforest is projected to fall about 57% by 2024 — from 0.05 in 2019 to a central estimate of 0.02 (95% range 0.00–0.17). A 5-year backtest shows a typical error of ±57%, with 100% of held-out values landing inside the 95% band.19702024
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 →
20200.030.000.18
20210.030.000.17
20220.030.000.17
20230.030.000.17
20240.020.000.17

Routes In Northern Pacific Rainforest

Routes recording Brewer's Sparrow in Northern Pacific Rainforest.
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 ShastaCALIFORNIA42019
RuchOREGON32000
Cool CampOREGON11970

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