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Species · California · BBS 2025 Release · 1966–2024

Swainson's Thrush Population Trend in California

All statesForest birds

Swainson's Thrush in California has edged down: down 19% on the route-weighted index since 1970.

-19%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 →
103Routes 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 Swainson's 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 →

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

Swainson's Thrush Population Forecast in California

If the recent trend holds, Swainson's Thrush in California is projected to rise about 35% by 2029 — from 2.0 in 2024 to a central estimate of 2.7 (95% range 1.5–3.9). A 5-year backtest shows a typical error of ±37.8%, with 100% of held-out values landing inside the 95% band.

+35%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 →
2.7Projected 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 →
1.5–3.995% 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 →
±37.8%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, Swainson's Thrush in California is projected to rise about 35% by 2029 — from 2.0 in 2024 to a central estimate of 2.7 (95% range 1.5–3.9). A 5-year backtest shows a typical error of ±37.8%, 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 →
20252.61.43.9
20262.71.43.9
20272.71.43.9
20282.71.53.9
20292.71.53.9

Swainson's Thrush Survey Routes in California

Routes recording Swainson's 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.6420101995
Point Reyes5920231970
Crescent Cty5820241972
Redwood N.P. 25220132012
Rio Dell5020121972
Korbel3920241972
Pescadero3020241992
Hiouchi3020142002
Holmes2520241968
Big Flat2020142002
Navarro1620111974
Fairfax1620241972
Honeydew1220171968
Fish Rock820141968
Morro Bay620191973
Lumberyard619891989
Calpella519811968
Bakersfield519701970
Santa Ynez519971969
Meadow Valley520241999
Cuyamaca Pk419721972
Laytonville420241972
Bodega Bay420191972
Orleans 2420142014
Moraga320101972

Swainson's Thrush Population Trend in Other States

alaskaarizonacoloradoconnecticutidahoillinoismainemarylandmassachusettsmichiganminnesotamontananebraskanevadanew-hampshirenew-mexiconew-yorknorth-carolinaoregonpennsylvaniasouth-dakotautahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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