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

Common Grackle Population Trend in Wisconsin

All statesGeneralists

Common Grackle in Wisconsin has fallen sharply: down 59% on the route-weighted index since 1968.

-59%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 Common Grackle 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 →

Common Grackle has fallen sharply in Wisconsin: down 59% on the route-weighted index since 1968.

Common Grackle Population Forecast in Wisconsin

If the recent trend holds, Common Grackle in Wisconsin is projected to fall about 45% by 2029 — from 16 in 2024 to a central estimate of 9.0 (95% range 0.00–26). A 5-year backtest shows a typical error of ±20.6%, with 100% of held-out values landing inside the 95% band.

-45%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 →
9.0Projected 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 →
0.00–2695% 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 →
±20.6%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, Common Grackle in Wisconsin is projected to fall about 45% by 2029 — from 16 in 2024 to a central estimate of 9.0 (95% range 0.00–26). A 5-year backtest shows a typical error of ±20.6%, 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 →
2025120.0029
2026110.0029
2027110.0028
20289.80.0027
20299.00.0026

Common Grackle Survey Routes in Wisconsin

Routes recording Common Grackle 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 →
Kiel10620221998
Omro8220011966
Mount Horeb7819901967
Pt Washingtn7620241966
Weyerhauser7520241966
Annaton6020241998
Raymond5220241966
Grimms5220211998
Stratford4320241966
Viroqua4220241966
Mukwonago4120041998
Verona4020241991
Brownsville3720241966
Eden3720241966
Holland3520241998
Hazel Green3420241966
Manitowoc3220241966
Hebron3220241966
Hudson3120241966
Trempealeau3120241966
Beloit2720241998
Stetsonville2420241990
Meridean2420241999
Newburg Crns2320241966
N Andover2320241967

Common Grackle Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawest-virginiawyoming

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