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Species · California · BBS 2025 Release · 1966–2024

Varied Thrush Population Trend in California

All statesForest birds

Varied Thrush in California has fallen sharply: down 65% on the route-weighted index since 1970.

-65%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 →
22Routes 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 Varied Thrush 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 declinecomputed 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 →

Varied Thrush has fallen sharply in California: down 65% on the route-weighted index since 1970.

Varied Thrush Population Forecast in California

If the recent trend holds, Varied Thrush in California is projected to rise about 160% by 2029 — from 0.13 in 2024 to a central estimate of 0.34 (95% range 0.00–0.73). A 5-year backtest shows a typical error of ±436.6%, with 80% of held-out values landing inside the 95% band.

+160%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 →
0.34Projected 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 →
0.00–0.7395% 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 →
±436.6%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, Varied Thrush in California is projected to rise about 160% by 2029 — from 0.13 in 2024 to a central estimate of 0.34 (95% range 0.00–0.73). A 5-year backtest shows a typical error of ±436.6%, with 80% 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 →
20250.330.000.72
20260.330.000.73
20270.330.000.73
20280.330.000.73
20290.340.000.73

Varied Thrush Survey Routes in California

Routes recording Varied Thrush 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 →
Redwood N.P. 26720132012
Redwood N.P.4920101995
Holmes1220241968
Rio Dell920121972
Burnt Ranch420161998
Big Flat220032003
Laytonville220001972
Bodega Bay220152014
Korbel220131974
Martins Fy220021982
Horse Creek120062006
Crescent Cty120221972
Honeydew119691968
Ship Mtn.120032001
Lonesome Rdg120042004
Pine Mountain120082008
Hay Fork120162001
Friday Ridge119991996
Lake Success119771975
Pescadero120131996
Waterman Gap120162004
Silver City119761976

Varied Thrush Population Trend in Other States

alaskaidahomontanaoregonwashington

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