BirdAnalyst
Species · Wisconsin · BBS 2026 Release · 1966–2025

Brown Thrasher Population Trend in Wisconsin

All statesForest birds

Brown Thrasher in Wisconsin has fallen sharply: down 54% on the route-weighted index since 1968.

-54%Since 1968TrendPercent 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 →
98Routes 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 →
59YearsYears 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 WisconsinNotable 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 Wisconsin: down 54% on the route-weighted index since 1968.

Brown Thrasher Population Forecast in Wisconsin

If the recent trend holds, Brown Thrasher in Wisconsin is projected to fall about 34% by 2030 — from 1.9 in 2025 to a central estimate of 1.2 (95% range 0.21–2.3). A 5-year backtest shows a typical error of ±28.8%, with 100% of held-out values landing inside the 95% band.

-34%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 →
1.2Projected 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 →
0.21–2.395% 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 →
±28.8%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 Wisconsin is projected to fall about 34% by 2030 — from 1.9 in 2025 to a central estimate of 1.2 (95% range 0.21–2.3). A 5-year backtest shows a typical error of ±28.8%, with 100% of held-out values landing inside the 95% band.19662030
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 →
20261.50.452.5
20271.40.392.5
20281.40.332.4
20291.30.272.3
20301.20.212.3

Brown Thrasher Survey Routes in Wisconsin

Routes recording Brown Thrasher in Wisconsin.
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 →
Annaton1220251998
Briggsville820251999
Trempealeau720251966
Dresser620251966
Stratford620251966
Hazel Green620251966
Wiota620251966
Hatfield519981970
N Andover520251967
Union Twp420251966
Weyerhauser420251966
Cochrane420251966
Omro420011966
Casco420251970
New Lisbon420251967
Raymond420251966
Meridean420251998
Gresham420251998
Iron River320251967
Minong320251967
Washington I320241967
Esdaile320251966
Stevens Pt320221966
Kendall320161967
Fall River320251966

Brown Thrasher Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawest-virginiawyoming

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