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

Bald Eagle Population Trend in Illinois

All statesGeneralists

Bald Eagle in Illinois has surged: up 18× on the route-weighted index since 2002.

18×Since 2002TrendPercent 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 →
49Routes 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 →
21YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Bald Eagle 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 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 →

Bald Eagle has surged in Illinois: up 18× on the route-weighted index since 2002.

Bald Eagle Population Forecast in Illinois

If the recent trend holds, Bald Eagle in Illinois is projected to stay roughly flat through 2029, near 0.21 (95% range 0.14–0.28). A 5-year backtest shows a typical error of ±35.9%, with 20% of held-out values landing inside the 95% band.

+6%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 →
0.21Projected 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 →
0.14–0.2895% 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 →
±35.9%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, Bald Eagle in Illinois is projected to stay roughly flat through 2029, near 0.21 (95% range 0.14–0.28). A 5-year backtest shows a typical error of ±35.9%, with 20% of held-out values landing inside the 95% band.20002029
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 →
20250.180.110.25
20260.190.120.26
20270.200.130.27
20280.200.130.27
20290.210.140.28

Bald Eagle Survey Routes in Illinois

Routes recording Bald Eagle 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 →
Belleview320242021
Beaverdam Lk320222018
Guilford220232021
Minonk220222019
Beaucoup220222014
Pulaski220222000
Camp Point220232018
Cherry Val 2220132013
Atkinson120242024
Geneseo120182009
Payson120242008
Sheffield120242024
Newark120222014
Gulfport120232023
Williamsfld120242019
Bartonville120162016
Fairbury120242022
Dailey120162016
Rosamond120242024
Janesville120232023
Bradbury120242024
Humboldt120242024
Lake Galena120192018
Lake Summerset120162014
Mascoutah Lk120242022

Bald Eagle Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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