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

Western Bluebird Population Trend in California

All statesForest birds

Western Bluebird in California has edged down: down 18% on the route-weighted index since 1970.

-18%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 →
189Routes 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 Western Bluebird 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 Western Bluebird in California. See the full index history below.

Western Bluebird Population Forecast in California

If the recent trend holds, Western Bluebird in California is projected to stay roughly flat through 2029, near 3.1 (95% range 2.0–4.2). A 5-year backtest shows a typical error of ±8.3%, with 100% of held-out values landing inside the 95% band.

-3%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 →
3.1Projected 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 →
2.0–4.295% 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 →
±8.3%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, Western Bluebird in California is projected to stay roughly flat through 2029, near 3.1 (95% range 2.0–4.2). A 5-year backtest shows a typical error of ±8.3%, with 100% 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 →
20253.12.04.2
20263.12.04.2
20273.12.04.2
20283.12.04.2
20293.12.04.2

Western Bluebird Survey Routes in California

Routes recording Western Bluebird 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 →
Tres Pinos 25720112005
Mt Pinos 23120242005
Valyermo2520191970
Cal Hot Spgs2520191993
White River2219921972
Adelaida2120241970
Redding2119831972
Deep Springs2019741974
Glen Ellen2020041972
Yolla Bolly1620241973
Jackson1419921972
Yokohl Val1319971972
Mark West1320241973
Big Bear1219861969
Tujunga1220211970
Coyote1220231972
Hat Creek1220181975
Lake Hemet1119861970
Alderpoint1120121974
Poloma1120241993
San Benito Mtn.1120092003
Red Bluff1020241968
Sisquoc1020141970
Honeydew920171968
Navarro920091973

Western Bluebird Population Trend in Other States

arizonacoloradoidahomontananevadanew-mexicooregontexasutahwashingtonwyoming

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