BirdAnalyst
Species · Illinois · BBS 2026 Release · 1966–2025

Indigo Bunting Population Trend in Illinois

All statesForest birds

Indigo Bunting in Illinois has surged: up 89% on the route-weighted index since 1968.

+89%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 →
105Routes 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 Indigo Bunting 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 →

Indigo Bunting has surged in Illinois: up 89% on the route-weighted index since 1968.

Indigo Bunting Population Forecast in Illinois

If the recent trend holds, Indigo Bunting in Illinois is projected to stay roughly flat through 2030, near 28 (95% range 21–34). A 5-year backtest shows a typical error of ±5.2%, with 100% of held-out values landing inside the 95% band.

+5%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 →
28Projected 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 →
21–3495% 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 →
±5.2%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, Indigo Bunting in Illinois is projected to stay roughly flat through 2030, near 28 (95% range 21–34). A 5-year backtest shows a typical error of ±5.2%, with 100% 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 →
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Indigo Bunting Survey Routes in Illinois

Routes recording Indigo Bunting 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 →
Belleview10220251966
Beaverdam Lk9220231970
Belknap8520251970
Pulaski8120251970
Brownville7620251993
Royalton6920252001
Brnt Prairie6720251976
Cave In Rock6520241993
Mt Vernon6220251971
Bremen6220251969
Sandusky5820231993
Eldred5620251993
Karnak5420252001
Athensville5220251971
Robinson4920231970
Camp Point4820251993
Gulfport4620251971
York4520251993
Melrose4019991973
Delwood4020251970
Concord3920251967
Athens3720251995
Janesville3320251972
Birds3320241976
Le Roy3320251993

Indigo Bunting Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.