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

Great Blue Heron Population Trend in Illinois

All statesWetland birds

Great Blue Heron in Illinois has surged: up 257% on the route-weighted index since 1968.

+257%Since 1968
105Routes In State
58Years

Notable Great Blue Heron Trends in Illinois

long arc increasecomputed index

Great Blue Heron has surged in Illinois: up 257% on the route-weighted index since 1968.

Great Blue Heron Population Forecast in Illinois

If the recent trend holds, Great Blue Heron in Illinois is projected to rise about 119% by 2029 — from 1.1 in 2024 to a central estimate of 2.4 (95% range 1.1–3.7). A 5-year backtest shows a typical error of ±92.7%, with 40% of held-out values landing inside the 95% band.

+119%Change by 2029
2.4Projected 2029 index
1.1–3.795% range
±92.7%Backtest error
19662029
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected index95% low95% high
20252.31.03.6
20262.31.13.6
20272.41.13.6
20282.41.13.7
20292.41.13.7

Great Blue Heron Survey Routes in Illinois

Routes recording Great Blue Heron in Illinois.
Gulfport620231973
Fairbury620241990
Gridley620242001
Humboldt520221991
Columbia520231967
Beaucoup520241972
Flora520241985
Cherry Val 2520182004
Wayne420241972
Melrose419991973
Concord420231994
Janesville420241994
Mascoutah Lk420241989
Seneca420241994
Sheffield320241981
Deer Creek320241985
Minonk320241992
Athensville320231973
Belleview320241966
Rosamond320212000
St Morgan320221994
Bremen320231970
Shannon320181993
Camp Point320241993
Barrington220081979

Great Blue Heron Population Trend in Other States

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

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