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

Little Blue Heron Population Trend in Illinois

All statesWetland birds

Little Blue Heron in Illinois has collapsed: down 86% on the route-weighted index since 1971.

-86%Since 1971TrendPercent 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 →
12Routes 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 Little Blue Heron Trends in IllinoisNotable 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 declinecomputed 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 →

Little Blue Heron has collapsed in Illinois: down 86% on the route-weighted index since 1971.

Little Blue Heron Population Forecast in Illinois

If the recent trend holds, Little Blue Heron in Illinois is projected to stay roughly flat through 2028, near 0.17 (95% range 0.00–0.48). A 5-year backtest shows a typical error of ±1100.3%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2028TrendPercent 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 →
0.17Projected 2028 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.4895% 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 →
±1100.3%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, Little Blue Heron in Illinois is projected to stay roughly flat through 2028, near 0.17 (95% range 0.00–0.48). A 5-year backtest shows a typical error of ±1100.3%, with 100% of held-out values landing inside the 95% band.19672028
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 →
20240.170.000.49
20250.170.000.49
20260.170.000.49
20270.170.000.49
20280.170.000.48

Little Blue Heron Survey Routes in Illinois

Routes recording Little Blue Heron in Illinois.
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 →
Belknap920112011
Bremen620172002
Pulaski420111970
Columbia320231987
Mascoutah Lk320151972
Sandusky220112001
Belleview119851976
Jamestown120121991
St Morgan120221967
Mt Vernon120062006
Olney120002000
Beaverdam Lk119941970

Little Blue Heron Population Trend in Other States

alabamaarkansasconnecticutdelawarefloridageorgiakansaskentuckylouisianamarylandmassachusettsmississippimissourinew-jerseynew-yorknorth-carolinanorth-dakotaoklahomapennsylvaniarhode-islandsouth-carolinatennesseetexasvirginia

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