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

Common Grackle Population Trend in Iowa

All statesGeneralists

Common Grackle in Iowa has declined: down 45% on the route-weighted index since 1969.

-45%Since 1969TrendPercent 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 →
39Routes 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 IowaNotable 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 Common Grackle in Iowa. See the full index history below.

Common Grackle Population Forecast in Iowa

If the recent trend holds, Common Grackle in Iowa is projected to rise about 65% by 2030 — from 31 in 2025 to a central estimate of 51 (95% range 28–73). A 5-year backtest shows a typical error of ±59.8%, with 60% of held-out values landing inside the 95% band.

+65%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 →
51Projected 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 →
28–7395% 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 →
±59.8%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 Iowa is projected to rise about 65% by 2030 — from 31 in 2025 to a central estimate of 51 (95% range 28–73). A 5-year backtest shows a typical error of ±59.8%, with 60% of held-out values landing inside the 95% band.19672030
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 →
2026512973
2027512973
2028512973
2029512973
2030512873

Common Grackle Survey Routes in Iowa

Routes recording Common Grackle in Iowa.
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 →
Desmoines11019791968
Titonka9920251968
Garner8519931971
Panther7820251967
Cedar Valley7419971967
Mccallsburg6920251996
College Spgs6520041967
Gaza5520251969
Davis Corner5120251968
Burchinal5120251995
Festina5020251968
Washington4920251967
Scranton4920251967
Rock Valley4920251968
Kanawha4320251967
Sioux City3920251968
Red Rock3120251968
Hudson3020251967
Dinsdale3020251968
Neola2820251968
Zearing2519951967
Clare2220191967
Pierson2220251968
Tipton2020251993
West Liberty1820251968

Common Grackle Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawest-virginiawisconsinwyoming

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