BirdAnalyst
Species · Wisconsin · BBS 2025 Release · 1966–2024

Brown Thrasher Population Trend in Wisconsin

All statesGeneralists

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 →
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 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 29% by 2029 — from 1.8 in 2024 to a central estimate of 1.3 (95% range 0.24–2.3). A 5-year backtest shows a typical error of ±32.8%, with 80% of held-out values landing inside the 95% band.

-29%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 →
1.3Projected 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 →
0.24–2.395% 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 →
±32.8%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 29% by 2029 — from 1.8 in 2024 to a central estimate of 1.3 (95% range 0.24–2.3). A 5-year backtest shows a typical error of ±32.8%, with 80% of held-out values landing inside the 95% band.19662029
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 →
20251.50.472.5
20261.50.412.5
20271.40.352.4
20281.30.292.4
20291.30.242.3

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 →
Buena Vista1420241998
Briggsville1020241999
N Andover820241967
Wiota820241966
Minong620241967
Cumberland620231966
Highland620241998
Beloit620231998
Hatfield519981970
N Freedom520241966
Meridean520231998
Gresham520241998
Weyerhauser420231966
Omro420011966
Casco420241970
Rolling Pr420241966
Hazel Green420241966
River Falls420241998
Annaton420241998
Union Twp320241966
Wausaukee320231980
Washington I320241967
Esdaile320241966
Cochrane320231966
Cadott320241966

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 2026-05-22.