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Species · Illinois · BBS 2025 Release · 1966–2024

Eastern Bluebird Population Trend in Illinois

All statesForest birds

Eastern Bluebird in Illinois has surged: up 81% on the route-weighted index since 1968.

+81%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 →
104Routes 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 →
58YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Eastern Bluebird 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 →

Eastern Bluebird has surged in Illinois: up 81% on the route-weighted index since 1968.

Eastern Bluebird Population Forecast in Illinois

If the recent trend holds, Eastern Bluebird in Illinois is projected to stay roughly flat through 2029, near 4.7 (95% range 2.1–7.3). A 5-year backtest shows a typical error of ±116.2%, with 60% of held-out values landing inside the 95% band.

+2%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 →
4.7Projected 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 →
2.1–7.395% 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 →
±116.2%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, Eastern Bluebird in Illinois is projected to stay roughly flat through 2029, near 4.7 (95% range 2.1–7.3). A 5-year backtest shows a typical error of ±116.2%, with 60% 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 →
20254.51.97.1
20264.61.97.2
20274.62.07.2
20284.72.07.3
20294.72.17.3

Eastern Bluebird Survey Routes in Illinois

Routes recording Eastern Bluebird 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 →
Delwood4320241970
Belknap3220241970
York1620241993
Bremen1520241969
Marshall1520242001
Flora1420241976
Royalton1220242001
Olney1120241966
Sandusky1120231993
Cave In Rock1120241993
Melrose1019991973
Clayton1020242001
Sheffield920241966
Dailey720221967
Bradbury720241970
Columbia720241966
Pulaski720241970
Beaverdam Lk720231970
Concord West720172001
Dudleyville720242001
Kell720242001
Mascoutah Lk620241970
St Morgan620221970
Mt Vernon620241971
Robinson620231971

Eastern Bluebird Population Trend in Other States

alabamaarizonaarkansascoloradoconnecticutdelawarefloridageorgiaindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsinwyoming

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