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Species · Wisconsin · BBS 2025 Release · 1966–2024

Brewer's Blackbird Population Trend in Wisconsin

All statesGeneralists

Brewer's Blackbird in Wisconsin has collapsed: down 84% on the route-weighted index since 1968.

-84%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 →
77Routes 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 Brewer's Blackbird 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 →

Brewer's Blackbird has collapsed in Wisconsin: down 84% on the route-weighted index since 1968.

Brewer's Blackbird Population Forecast in Wisconsin

If the recent trend holds, Brewer's Blackbird in Wisconsin is projected to fall about 31% by 2029 — from 0.33 in 2024 to a central estimate of 0.23 (95% range 0.00–1.8). A 5-year backtest shows a typical error of ±157.5%, with 100% of held-out values landing inside the 95% band.

-31%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 →
0.23Projected 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 →
0.00–1.895% 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 →
±157.5%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, Brewer's Blackbird in Wisconsin is projected to fall about 31% by 2029 — from 0.33 in 2024 to a central estimate of 0.23 (95% range 0.00–1.8). A 5-year backtest shows a typical error of ±157.5%, with 100% 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 →
20250.500.002.1
20260.430.002.0
20270.370.002.0
20280.300.001.9
20290.230.001.8

Brewer's Blackbird Survey Routes in Wisconsin

Routes recording Brewer's Blackbird 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 →
Loraine2220051966
Shanagolden1719841969
Stratford920131968
Amnicon Falls920181998
Merrill820151966
Stetsonville820241990
River Falls720131999
Irma620101967
Manawa620141969
Mount Horeb619701970
Buena Vista620241998
Cumberland520181967
Exeland520231968
Crandon520161967
Viroqua519761976
Princeton519931986
Couderay420111969
Holway419891967
Gilmanton419881988
Unity420231967
Pardeeville420221968
Flambeau420241999
Cavour420211999
Meridean420192002
Gresham420111998

Brewer's Blackbird Population Trend in Other States

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