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Species · Illinois · BBS 2025 Release · 1966–2024

Black-crowned Night Heron Population Trend in Illinois

All statesWetland birds

Black-crowned Night Heron in Illinois has declined: down 34% on the route-weighted index since 1968.

-34%Since 1968TrendPercent 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 →
20Routes 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 →
45YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Black-crowned Night 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 →

No notable trend signals for Black-crowned Night Heron in Illinois. See the full index history below.

Black-crowned Night Heron Population Forecast in Illinois

If the recent trend holds, Black-crowned Night Heron in Illinois is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.13). A 5-year backtest shows a typical error of ±63.4%, with 100% of held-out values landing inside the 95% band.

n/aChange 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 →
0.01Projected 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 →
0.00–0.1395% 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 →
±63.4%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, Black-crowned Night Heron in Illinois is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.13). A 5-year backtest shows a typical error of ±63.4%, with 100% of held-out values landing inside the 95% band.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 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 →
20250.010.000.13
20260.010.000.13
20270.010.000.13
20280.010.000.13
20290.010.000.13

Black-crowned Night Heron Survey Routes in Illinois

Routes recording Black-crowned Night 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 →
Bartonville719991990
Jamestown519951974
Bluff Spgs419741974
Royalton320232023
New Lenox219881966
Columbia220001972
Guilford119811981
Barrington119951981
Itasca120241986
Geneseo119941971
Sheffield119921992
Wayne120101967
Sherburnvill120151990
Deer Creek119951995
Athensville119881982
Belleview119821982
Mascoutah Lk120051991
St Morgan120081993
Yorkville120162009
Pulaski119781978

Black-crowned Night Heron Population Trend in Other States

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

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