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Species · California · BBS 2025 Release · 1966–2024

Williamson's Sapsucker Population Trend in California

All statesForest birds

Williamson's Sapsucker in California has increased: up 40% on the route-weighted index since 1975.

+40%Since 1975TrendPercent 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 →
32Routes 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 →
47YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Williamson's Sapsucker 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 →

No notable trend signals for Williamson's Sapsucker in California. See the full index history below.

Williamson's Sapsucker Population Forecast in California

If the recent trend holds, Williamson's Sapsucker in California is projected to stay roughly flat through 2029, near 0.12 (95% range 0.03–0.21). A 5-year backtest shows a typical error of ±219.3%, with 60% of held-out values landing inside the 95% band.

n/aChange 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 →
0.12Projected 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 →
0.03–0.2195% 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 →
±219.3%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, Williamson's Sapsucker in California is projected to stay roughly flat through 2029, near 0.12 (95% range 0.03–0.21). A 5-year backtest shows a typical error of ±219.3%, with 60% of held-out values landing inside the 95% band.19722029
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 →
20250.110.020.20
20260.110.020.20
20270.110.020.20
20280.120.020.21
20290.120.030.21

Williamson's Sapsucker Survey Routes in California

Routes recording Williamson's Sapsucker 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 →
Lakeshore420041972
Hackamore320102000
Green Valley220152015
Eagle Lake219851985
Dardanelle220041973
Crowley Lake220161975
Tuolumne Grove220142000
Goumaz220111997
Little Truckee220231997
Pine Mountain220171998
Crestview220241997
Downieville219751975
Valyermo220131995
Nubieber120021999
Lassen Park119761976
Whiskeytown120062006
Tionesta120211997
Sattley120191997
Paxton120172017
Pollock Pines120132012
Davis Creek119941994
Macdoel120112011
Medicine Mtn.120212001
Mt Shasta120121976
Cedarville120151978

Williamson's Sapsucker Population Trend in Other States

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