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

Brown-headed Cowbird Population Trend in Wisconsin

All statesGeneralists

Brown-headed Cowbird in Wisconsin has declined: down 45% on the route-weighted index since 1968.

-45%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-headed Cowbird 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 →

No notable trend signals for Brown-headed Cowbird in Wisconsin. See the full index history below.

Brown-headed Cowbird Population Forecast in Wisconsin

If the recent trend holds, Brown-headed Cowbird in Wisconsin is projected to fall about 11% by 2030 — from 12 in 2025 to a central estimate of 10 (95% range 6.5–14). A 5-year backtest shows a typical error of ±9.1%, with 100% of held-out values landing inside the 95% band.

-11%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 →
10Projected 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 →
6.5–1495% 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 →
±9.1%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-headed Cowbird in Wisconsin is projected to fall about 11% by 2030 — from 12 in 2025 to a central estimate of 10 (95% range 6.5–14). A 5-year backtest shows a typical error of ±9.1%, 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 →
2026117.215
2027117.115
2028116.914
2029106.714
2030106.514

Brown-headed Cowbird Survey Routes in Wisconsin

Routes recording Brown-headed Cowbird 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 →
Grimms9620211998
River Falls5120251998
Pt Washingtn4320241966
Paris3620251966
Cadott3220251966
Pardeeville3220251967
Weyerhauser3020251966
Annaton3020251998
Loraine2920251966
Hazel Green2920251966
Cochrane2820251966
New Lisbon2720251967
Raymond2720251966
Omro2620011966
Fall River2620251966
N Freedom2420251966
Beloit2220251998
Holland2120251998
Dresser2020251966
Holway2019891967
Wiota2020251966
N Andover1920251967
Kiel1920251998
Mukwonago1920041998
Mukwonago 21920252005

Brown-headed Cowbird Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawyoming

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