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

Green Heron Population Trend in Iowa

All statesWetland birds

Green Heron in Iowa has edged down: down 14% on the route-weighted index since 1970.

-14%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 →
32Routes 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 →
49YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Green 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 →

No notable trend signals for Green Heron in Iowa. See the full index history below.

Green Heron Population Forecast in Iowa

If the recent trend holds, Green Heron in Iowa is projected to fall about 21% by 2029 — from 0.14 in 2024 to a central estimate of 0.11 (95% range 0.00–0.23). A 5-year backtest shows a typical error of ±85%, with 100% of held-out values landing inside the 95% band.

-21%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 →
0.11Projected 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 →
0.00–0.2395% 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 →
±85%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, Green Heron in Iowa is projected to fall about 21% by 2029 — from 0.14 in 2024 to a central estimate of 0.11 (95% range 0.00–0.23). A 5-year backtest shows a typical error of ±85%, with 100% of held-out values landing inside the 95% band.19682029
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 →
20250.110.000.23
20260.110.000.23
20270.110.000.23
20280.110.000.23
20290.110.000.23

Green Heron Survey Routes in Iowa

Routes recording Green 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 →
Davis Corner320051976
Exline220211976
Melrose220241988
Red Rock220031969
Washington219931980
Garner219921992
Gaza220011983
Tipton219941994
Mt Hamill120221972
Bedford120151972
College Spgs119711971
Bryant120071986
West Liberty119761976
Brooklyn119931970
Williamsburg119931970
Panther119991977
Wales119761976
Maquoketa119961973
Alice119991968
Prairieburg120121968
Hudson120211968
Dinsdale119921985
Kanawha119891977
Zearing119941971
Scranton119831983

Green Heron Population Trend in Other States

alabamaarizonaarkansascaliforniaconnecticutdelawarefloridageorgiaillinoisindianakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawashingtonwest-virginiawisconsin

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