BirdAnalyst
Species · California · BBS 2025 Release · 1966–2024

Acorn Woodpecker Population Trend in California

All statesForest birds

Acorn Woodpecker in California has risen sharply: up 54% on the route-weighted index since 1970.

+54%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 →
166Routes 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 →
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 Acorn Woodpecker 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 →

Acorn Woodpecker has risen sharply in California: up 54% on the route-weighted index since 1970.

Acorn Woodpecker Population Forecast in California

If the recent trend holds, Acorn Woodpecker in California is projected to stay roughly flat through 2029, near 13 (95% range 9.7–17). A 5-year backtest shows a typical error of ±14.6%, with 60% of held-out values landing inside the 95% band.

-6%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 →
13Projected 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 →
9.7–1795% 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 →
±14.6%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, Acorn Woodpecker in California is projected to stay roughly flat through 2029, near 13 (95% range 9.7–17). A 5-year backtest shows a typical error of ±14.6%, with 60% 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 →
2025139.516
2026139.616
2027139.616
2028139.716
2029139.717

Acorn Woodpecker Survey Routes in California

Routes recording Acorn Woodpecker 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 →
Mt Laguna11119871970
Bass Lake9020191972
Yolla Bolly9020241973
Red Bluff8720241968
White River8419921972
Lockwood8220241972
Yokohl Val7219971972
Fairfax6520241972
Lake Berryessa6220242023
Coalinga6020221973
Orange Cove6020161972
Greenhorn Mt6020081971
Cal Hot Spgs6020191993
Waterman Gap5620241972
Tehama5220221973
Lake Hemet5019861970
Parkfield4920241968
Silver City4920131972
Sanger4820242011
Santa Ynez4720191969
Adelaida4720241970
Coyote4620241972
Cleveland Nf 24520222019
Ono4420121984
Angelus Oaks4420171989

Acorn Woodpecker Population Trend in Other States

arizonanew-mexicooregontexas

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