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Species · California · BBS 2025 Release · 1966–2024

California Thrasher Population Trend in California

All statesGeneralists

California Thrasher in California has held roughly steady: down 4% on the route-weighted index since 1970.

-4%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 →
115Routes 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 California Thrasher 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 California Thrasher in California. See the full index history below.

California Thrasher Population Forecast in California

If the recent trend holds, California Thrasher in California is projected to fall about 54% by 2029 — from 1.7 in 2024 to a central estimate of 0.79 (95% range 0.00–1.9). A 5-year backtest shows a typical error of ±60.8%, with 60% of held-out values landing inside the 95% band.

-54%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 →
0.79Projected 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 →
0.00–1.995% 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 →
±60.8%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, California Thrasher in California is projected to fall about 54% by 2029 — from 1.7 in 2024 to a central estimate of 0.79 (95% range 0.00–1.9). A 5-year backtest shows a typical error of ±60.8%, 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 →
20250.850.002.0
20260.830.002.0
20270.820.002.0
20280.810.002.0
20290.790.001.9

California Thrasher Survey Routes in California

Routes recording California Thrasher 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 →
Elsinore Mtn4120241970
Lake Cachuma3720161972
Cuyamaca Pk2720241970
Rumsey1920081969
Mt Baldy1820241970
Oak Grove1620241968
Poway1219801973
Lockwood Val1120191970
Anza1120041970
Colma1019711968
Jacumba1020241973
Anza 21020242005
Cleveland Nf 21020222019
Fallsvale819811974
Elizabeth Lk720161970
Yolla Bolly720241973
Hough Springs720071999
Folsom620241984
Mesa Grande620241970
Greenfield620241973
Tomhead620111998
Stonyford620182015
Foster Park519941969
Green Valley520231972
Tres Pinos 2520112005

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