BirdAnalyst
Species · BCR 9 · BBS 2026 Release · 1966–2025

Varied Thrush In Great Basin

All regionsGreat BasinForest birds

Varied Thrush in Great Basin has fallen sharply: down 51% on the route-weighted index since 1970.

-51%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 →
31Routes 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 →
57YearsYears 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 →

Varied Thrush has fallen sharply in Great Basin: down 51% on the route-weighted index since 1970.

Varied Thrush In Great Basin Population Forecast

If the recent trend holds, Varied Thrush in Great Basin is projected to rise about 32% by 2030 — from 0.39 in 2025 to a central estimate of 0.51 (95% range 0.00–1.5). A 5-year backtest shows a typical error of ±82.7%, with 100% of held-out values landing inside the 95% band.

+32%Change by 2030TrendPercent 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 →
0.51Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–1.595% 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 →
±82.7%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 Great Basin is projected to rise about 32% by 2030 — from 0.39 in 2025 to a central estimate of 0.51 (95% range 0.00–1.5). A 5-year backtest shows a typical error of ±82.7%, with 100% of held-out values landing inside the 95% band.19682030
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 →
20260.560.001.5
20270.550.001.5
20280.540.001.5
20290.530.001.5
20300.510.001.5

Routes In Great Basin

Routes recording Varied Thrush in Great Basin.
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 →
White ChuckWASHINGTON272025
Cascade RivWASHINGTON212006
GlacierWASHINGTON172024
IndexWASHINGTON131997
RimrockWASHINGTON102025
IndexWASHINGTON81971
SnowdenWASHINGTON81973
Suiattle RivWASHINGTON72019
JosephOREGON51984
Index 2WASHINGTON52023
No CascadesWASHINGTON52019
KendallWASHINGTON42024
Blewett PassWASHINGTON42025
NewhalemWASHINGTON32025
WinthropWASHINGTON31999
L. WenatcheeWASHINGTON32025
ConcreteWASHINGTON32025
Camp ShermanOREGON21986
Davis LakeOREGON22001
SistersOREGON22012
TwispWASHINGTON22008
CarltonWASHINGTON21999
MazamaWASHINGTON22022
E. Mt. AdamsWASHINGTON22011
Barnes ValOREGON11971

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.