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

American Dipper Population Trend in California

All statesGeneralists

American Dipper in California has declined: down 32% on the route-weighted index since 1973.

-32%Since 1973TrendPercent 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 →
48Routes 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 →
53YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable American Dipper 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 American Dipper in California. See the full index history below.

American Dipper Population Forecast in California

If the recent trend holds, American Dipper in California is projected to fall about 25% by 2029 — from 0.07 in 2024 to a central estimate of 0.05 (95% range 0.00–0.11). A 5-year backtest shows a typical error of ±92.5%, with 100% of held-out values landing inside the 95% band.

-25%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 →
0.05Projected 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 →
0.00–0.1195% 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 →
±92.5%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, American Dipper in California is projected to fall about 25% by 2029 — from 0.07 in 2024 to a central estimate of 0.05 (95% range 0.00–0.11). A 5-year backtest shows a typical error of ±92.5%, with 100% of held-out values landing inside the 95% band.19702029
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 →
20250.050.000.12
20260.050.000.11
20270.050.000.11
20280.050.000.11
20290.050.000.11

American Dipper Survey Routes in California

Routes recording American Dipper 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 →
Whiskeytown520072002
Fallsvale319751975
Green Valley220122012
Kings Canyon220241974
Hiouchi220122002
Bass Lake219741974
Meadow Valley220242004
Orleans220121973
Big Flat220022002
Hay Fork220052001
Butte Meadow220001972
Korbel220211980
Woodfords220241973
Horse Creek120181980
Carrville119701970
Honeydew120081972
Holmes119781978
Iron Gate119961993
Gazelle120181991
Dardanelle120181977
Dirigio120141999
Likely119841982
Redwood N.P. 2120132013
Tuolumne Grove120181972
Paxton120222001

American Dipper Population Trend in Other States

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