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

Indigo Bunting Population Trend in Illinois

All statesGeneralists

Indigo Bunting in Illinois has surged: up 88% on the route-weighted index since 1968.

+88%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 →
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 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 88% 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 2029, near 28 (95% range 21–34). A 5-year backtest shows a typical error of ±8.5%, with 100% of held-out values landing inside the 95% band.

-5%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 →
28Projected 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 →
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 →
±8.5%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 2029, near 28 (95% range 21–34). A 5-year backtest shows a typical error of ±8.5%, 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 →
2025272134
2026282134
2027282134
2028282134
2029282134

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 →
Royalton12320242001
Belleview10220241966
Belknap9720241970
Beaverdam Lk9220231970
Karnak8520242001
Eldred8320211993
Brnt Prairie7320241976
Brownville6820241993
Pulaski6720241970
Cave In Rock6520241993
Bremen5920241969
Athensville5820241971
York5820241993
Sandusky5820231993
Chandlervill5020241971
Robinson4920231970
Camp Point4720241993
Mt Vernon4620241971
Melrose4019991973
Concord4020241967
Delwood4020241970
Payson3820242000
Mascoutah Lk3620241967
Marshall3620242001
Humphrey3520241972

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 2026-05-22.