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

Brown-headed Cowbird Population Trend in Wisconsin

All statesGeneralists

Brown-headed Cowbird in Wisconsin has declined: down 43% on the route-weighted index since 1968.

-43%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-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 15% by 2029 — from 12 in 2024 to a central estimate of 10 (95% range 6.6–14). A 5-year backtest shows a typical error of ±9%, with 100% of held-out values landing inside the 95% band.

-15%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 →
10Projected 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 →
6.6–1495% 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%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 15% by 2029 — from 12 in 2024 to a central estimate of 10 (95% range 6.6–14). A 5-year backtest shows a typical error of ±9%, 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 →
2025117.315
2026117.115
2027117.015
2028116.814
2029106.614

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
Pardeeville5420241967
Annaton4820241998
Pt Washingtn4320241966
Paris4120241966
Hebron3620241966
Raymond3620241966
River Falls3520241998
Kiel3520221998
Weyerhauser3320241966
Cumberland3220241966
Hazel Green3020241966
Cadott2920241966
Holland2920241998
Stratford2820241966
Fall River2820241966
Omro2620011966
Union Twp2320241966
Dresser2220241966
Wiota2120241966
Holway2019891967
Saxeville2020241966
Mukwonago 22020242005
N Andover1920241967
Mukwonago1920041998

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 2026-05-22.