BirdAnalyst
Species · California · BBS 2026 Release · 1966–2025

Brown Creeper Population Trend in California

All statesForest birds

Brown Creeper in California has surged: up 329% on the route-weighted index since 1970.

+329%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 →
129Routes In StateSurvey 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 Brown Creeper Trends in CaliforniaNotable 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 →

Brown Creeper has surged in California: up 328% on the route-weighted index since 1970.

Brown Creeper Population Forecast in California

If the recent trend holds, Brown Creeper in California is projected to rise about 22% by 2030 — from 1.6 in 2025 to a central estimate of 1.9 (95% range 1.4–2.4). A 5-year backtest shows a typical error of ±30.9%, with 60% of held-out values landing inside the 95% band.

+22%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 →
1.9Projected 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 →
1.4–2.495% 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 →
±30.9%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, Brown Creeper in California is projected to rise about 22% by 2030 — from 1.6 in 2025 to a central estimate of 1.9 (95% range 1.4–2.4). A 5-year backtest shows a typical error of ±30.9%, with 60% 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 →
20261.81.32.4
20271.91.32.4
20281.91.42.4
20291.91.42.4
20301.91.42.4

Brown Creeper Survey Routes in California

Routes recording Brown Creeper in 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 →
Westville1820251971
Last Chance1520191994
Lumberyard1420251976
Holmes1320251969
Lassen Park1319891972
Waterman Gap1320251972
Greenhorn Mt1220081971
Friday Ridge1020251995
Point Reyes920251970
Riverton920251973
Whiskeytown920132002
Crowder Flat920192002
Pollock Pines920251998
Fish Rock820141968
Fairfax820241972
Butte Meadow820141972
Lakeshore820241972
Coulterville820191997
Chilcoot720241998
Laytonville620251973
Offield Mtn520141977
Bartle520211972
Tahoe Nf519941993
Redwood N.P. 2420132012
Big Bear419831969

Brown Creeper Population Trend in Other States

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