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

Great Blue Heron Population Trend in Iowa

All statesWetland birds

Great Blue Heron in Iowa has surged: up 542% on the route-weighted index since 1970.

+542%Since 1970TrendPercent 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 →
38Routes 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 Great Blue Heron 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 →

long arc increasecomputed 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 →

Great Blue Heron has surged in Iowa: up 542% on the route-weighted index since 1970.

Great Blue Heron Population Forecast in Iowa

If the recent trend holds, Great Blue Heron in Iowa is projected to rise about 54% by 2030 — from 0.77 in 2025 to a central estimate of 1.2 (95% range 0.56–1.8). A 5-year backtest shows a typical error of ±141.7%, with 0% of held-out values landing inside the 95% band.

+54%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 →
1.2Projected 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 →
0.56–1.895% 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 →
±141.7%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, Great Blue Heron in Iowa is projected to rise about 54% by 2030 — from 0.77 in 2025 to a central estimate of 1.2 (95% range 0.56–1.8). A 5-year backtest shows a typical error of ±141.7%, with 0% of held-out values landing inside the 95% band.19682030
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 →
20261.10.491.8
20271.10.511.8
20281.20.521.8
20291.20.541.8
20301.20.561.8

Great Blue Heron Survey Routes in Iowa

Routes recording Great Blue Heron 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 →
College Spgs 2520252005
Mt Hamill420251985
Mccallsburg420141997
Desmoines319781978
Panther320181994
Zearing319951989
Exline220251974
Bedford220251986
Cedar Valley219891971
Red Rock220241988
Washington220231980
Neola220161992
Maquoketa220141974
Kanawha220241990
Scranton220251976
Sioux City220241977
Festina220251969
Davis Corner220251968
Melrose120251974
College Spgs120042003
Bryant120251970
West Liberty120241983
Brooklyn120171998
Williamsburg120231991
Wales120172002

Great Blue Heron Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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