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Species · South Dakota · BBS 2025 Release · 1966–2024

Swainson's Thrush Population Trend in South Dakota

All statesForest birds

Swainson's Thrush in South Dakota has surged: up 18× on the route-weighted index since 1972.

18×Since 1972TrendPercent 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 →
13Routes 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 →
50YearsYears 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 South DakotaNotable 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 increasecomputed 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 →

Swainson's Thrush has surged in South Dakota: up 18× on the route-weighted index since 1972.

Swainson's Thrush Population Forecast in South Dakota

If the recent trend holds, Swainson's Thrush in South Dakota is projected to stay roughly flat through 2029, near 1.8 (95% range 0.09–3.5). A 5-year backtest shows a typical error of ±129%, with 100% of held-out values landing inside the 95% band.

-3%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 →
1.8Projected 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 →
0.09–3.595% 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 →
±129%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 South Dakota is projected to stay roughly flat through 2029, near 1.8 (95% range 0.09–3.5). A 5-year backtest shows a typical error of ±129%, with 100% of held-out values landing inside the 95% band.19692029
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 →
20251.70.003.4
20261.70.013.5
20271.80.033.5
20281.80.063.5
20291.80.093.5

Swainson's Thrush Survey Routes in South Dakota

Routes recording Swainson's Thrush in South Dakota.
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 →
Long Draw3620241992
Black Fox3120171992
Norbeck2920021992
Englewood1720211992
Rochford1420181996
Silver City620121993
Custer520241970
Lightning Cr220002000
Hazelrodt120221995
Hill City120131996
Elk Mountain120041998
Wind Cave Np120132013
Roubaix Lk119901969

Swainson's Thrush Population Trend in Other States

alaskaarizonacaliforniacoloradoconnecticutidahoillinoismainemarylandmassachusettsmichiganminnesotamontananebraskanevadanew-hampshirenew-mexiconew-yorknorth-carolinaoregonpennsylvaniautahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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