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Species · Illinois · BBS 2026 Release · 1966–2025

Eastern Bluebird Population Trend in Illinois

All statesForest birds

Eastern Bluebird in Illinois has surged: up 123% on the route-weighted index since 1968.

+123%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 →
59YearsYears 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 123% 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 2030, near 4.7 (95% range 2.1–7.4). A 5-year backtest shows a typical error of ±107.9%, with 60% of held-out values landing inside the 95% band.

+4%Change by 2030TrendPercent 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 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
2.1–7.495% 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 →
±107.9%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, Eastern Bluebird in Illinois is projected to stay roughly flat through 2030, near 4.7 (95% range 2.1–7.4). A 5-year backtest shows a typical error of ±107.9%, with 60% of held-out values landing inside the 95% band.19662030
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 →
20264.61.97.2
20274.62.07.2
20284.72.07.3
20294.72.17.3
20304.72.17.4

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 →
Pulaski2720251970
Belknap2620251970
Bremen2020251969
Royalton1820252001
Terre Haute1720251966
Bradbury1720251970
Karnak1720252001
Jamestown1520251969
Flora1420241976
Delwood1220251970
Mt Vernon1120251971
Olney1120241966
Sandusky1120231993
Cave In Rock1120241993
Dudleyville1120252001
Melrose1019991973
Sheffield920241966
York920251993
Eubanks820252001
Bartonville720251973
Athensville720251971
Beaverdam Lk720231970
Camp Point720251993
Keithsburg720252001
Concord West720172001

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 2026-08-14.