BirdAnalyst
Species · South Dakota · BBS 2026 Release · 1966–2025

Brown Thrasher Population Trend in South Dakota

All statesForest birds

Brown Thrasher in South Dakota has fallen sharply: down 52% on the route-weighted index since 1969.

-52%Since 1969TrendPercent 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 →
56Routes 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 →
58YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Brown Thrasher 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 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 →

Brown Thrasher has fallen sharply in South Dakota: down 52% on the route-weighted index since 1969.

Brown Thrasher Population Forecast in South Dakota

If the recent trend holds, Brown Thrasher in South Dakota is projected to fall about 36% by 2030 — from 2.1 in 2025 to a central estimate of 1.4 (95% range 0.16–2.6). A 5-year backtest shows a typical error of ±20.4%, with 100% of held-out values landing inside the 95% band.

-36%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 →
1.4Projected 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 →
0.16–2.695% 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 →
±20.4%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, Brown Thrasher in South Dakota is projected to fall about 36% by 2030 — from 2.1 in 2025 to a central estimate of 1.4 (95% range 0.16–2.6). A 5-year backtest shows a typical error of ±20.4%, with 100% of held-out values landing inside the 95% band.19672030
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 →
20261.50.302.7
20271.50.262.7
20281.40.232.7
20291.40.192.6
20301.40.162.6

Brown Thrasher Survey Routes in South Dakota

Routes recording Brown Thrasher 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 →
Rosebud1220111967
Chamberlain820111967
Volga720251967
Reva720251979
Ft Thompson620111967
Britton620231967
Conde619841968
Gettysburg620231970
Maurine620251968
White Lake520111967
Laplant520111971
Ottumwa520251967
Gorman520091979
Lodgepole520251995
Isabel520131990
White River520141994
Lane419991967
Veblen420231967
Promise420141971
Harding420251968
Cedar Pass420251968
Marcus420141999
Lacreek420251991
Tripp320251967
Roswell320141967

Brown Thrasher Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinatennesseetexasvermontvirginiawest-virginiawisconsinwyoming

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