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

Common Grackle Population Trend in Wisconsin

All statesGeneralists

Common Grackle in Wisconsin has fallen sharply: down 61% on the route-weighted index since 1968.

-61%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 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 61% 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 46% by 2030 — from 16 in 2025 to a central estimate of 8.6 (95% range 0.00–26). A 5-year backtest shows a typical error of ±26%, with 100% of held-out values landing inside the 95% band.

-46%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 →
8.6Projected 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 →
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 →
±26%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 46% by 2030 — from 16 in 2025 to a central estimate of 8.6 (95% range 0.00–26). A 5-year backtest shows a typical error of ±26%, 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 →
2026120.0029
2027110.0028
2028100.0027
20299.40.0026
20308.60.0026

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 →
Omro8220011966
Mount Horeb7819901967
Pt Washingtn7620241966
Weyerhauser7520251966
Trempealeau7520251966
Annaton7520251998
Eden6520251966
Grimms5220211998
River Falls4920251998
Brownsville4820251966
Viroqua4220241966
Hazel Green4220251966
Mukwonago4120041998
Raymond3920251966
Fall River3520251966
Meridean3420251999
Unity3220251967
Manitowoc3220241966
Holland2920251998
N Andover2820251967
Stratford2720251966
Hebron2720251966
Rolling Pr2620251966
Hudson2520251966
Clintonville2420251967

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 2026-08-14.