BirdAnalyst
Species · BCR 15 · BBS 2025 Release · 1966–2024

American Dipper In Sierra Nevada

All regionsSierra NevadaGeneralists

American Dipper in Sierra Nevada has fallen sharply: down 58% on the route-weighted index since 1974.

-58%Since 1974TrendPercent 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 →
18Routes In RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
51YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable 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 →

American Dipper has fallen sharply in Sierra Nevada: down 58% on the route-weighted index since 1974.

American Dipper In Sierra Nevada Population Forecast

If the recent trend holds, American Dipper in Sierra Nevada is projected to fall about 77% by 2029 — from 0.32 in 2024 to a central estimate of 0.07 (95% range 0.00–0.32). A 5-year backtest shows a typical error of ±54.6%, with 80% of held-out values landing inside the 95% band.

-77%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 →
0.07Projected 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 →
0.00–0.3295% 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 →
±54.6%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, American Dipper in Sierra Nevada is projected to fall about 77% by 2029 — from 0.32 in 2024 to a central estimate of 0.07 (95% range 0.00–0.32). A 5-year backtest shows a typical error of ±54.6%, with 80% of held-out values landing inside the 95% band.19722029
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 →
20250.100.000.34
20260.090.000.34
20270.090.000.33
20280.080.000.32
20290.070.000.32

Routes In Sierra Nevada

Routes recording American Dipper in Sierra Nevada.
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 →
Bass LakeCALIFORNIA21974
WoodfordsCALIFORNIA22024
Kings CanyonCALIFORNIA22024
Butte MeadowCALIFORNIA22000
Meadow ValleyCALIFORNIA22024
DardanelleCALIFORNIA12018
JohnsvilleCALIFORNIA12019
LumberyardCALIFORNIA12007
Tuolumne GroveCALIFORNIA12018
GeneseeCALIFORNIA12023
DownievilleCALIFORNIA12017
RivertonCALIFORNIA12012
Hat CreekCALIFORNIA12016
LakeshoreCALIFORNIA11997
Chaos CraterCALIFORNIA12001
PaxtonCALIFORNIA12022
WawonaCALIFORNIA11998
ChilcootCALIFORNIA12009

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