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

Common Grackle Population Trend in Iowa

All statesGeneralists

Common Grackle in Iowa has declined: down 42% on the route-weighted index since 1969.

-42%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 →
57YearsYears 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 26% by 2029 — from 42 in 2024 to a central estimate of 52 (95% range 31–74). A 5-year backtest shows a typical error of ±49.7%, with 40% of held-out values landing inside the 95% band.

+26%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 →
52Projected 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 →
31–7495% 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 →
±49.7%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 26% by 2029 — from 42 in 2024 to a central estimate of 52 (95% range 31–74). A 5-year backtest shows a typical error of ±49.7%, with 40% of held-out values landing inside the 95% band.19672029
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 →
2025533174
2026533174
2027533174
2028533174
2029523174

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 →
Mccallsburg11320241996
Desmoines11019791968
Kanawha10520241967
Scranton9620241967
Gaza8720231969
Rock Valley8720241968
Garner8519931971
Cedar Valley7419971967
Panther7220241967
Sioux City6820241968
College Spgs6520041967
Titonka6220241968
Washington5920241967
Hudson5420221967
Pierson4920191968
Burchinal4320241995
Tipton3420241993
Red Rock3220241968
Davis Corner3020241968
College Spgs 23020232005
Dinsdale2920241968
Festina2820241968
Zearing2519951967
Clare2220191967
Neola2020161968

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 2026-05-22.