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Species · Illinois · BBS 2026 Release · 1966–2025

Carolina Chickadee Population Trend in Illinois

All statesForest birds

Carolina Chickadee in Illinois has surged: up 431% on the route-weighted index since 1968.

+431%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 →
40Routes 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 Carolina Chickadee 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 →

Carolina Chickadee has surged in Illinois: up 431% on the route-weighted index since 1968.

Carolina Chickadee Population Forecast in Illinois

If the recent trend holds, Carolina Chickadee in Illinois is projected to fall about 17% by 2030 — from 1.8 in 2025 to a central estimate of 1.5 (95% range 0.93–2.0). A 5-year backtest shows a typical error of ±20.1%, with 80% of held-out values landing inside the 95% band.

-17%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 →
1.5Projected 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 →
0.93–2.095% 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 →
±20.1%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, Carolina Chickadee in Illinois is projected to fall about 17% by 2030 — from 1.8 in 2025 to a central estimate of 1.5 (95% range 0.93–2.0). A 5-year backtest shows a typical error of ±20.1%, with 80% 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 →
20261.40.871.9
20271.40.882.0
20281.40.902.0
20291.50.922.0
20301.50.932.0

Carolina Chickadee Survey Routes in Illinois

Routes recording Carolina Chickadee 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 →
Mt Vernon2920251971
Belknap2520251970
Bremen1620251969
St Morgan1020221967
Birds820241976
Cave In Rock820241993
Pulaski720251971
Royalton720252001
York720251993
Mascoutah Lk620241978
Beaucoup620251972
Delwood520251970
Grape Creek420252001
Bradbury420251970
Brnt Prairie420251977
Brownville420251993
Janesville320251995
Beaverdam Lk320231970
Dudleyville320252001
Jamestown220251967
Olney220241966
Flora220191976
Robinson220231971
Marshall220252006
Kell220252001

Carolina Chickadee Population Trend in Other States

alabamaarkansasdelawarefloridageorgiaindianakansaskentuckylouisianamarylandmississippimissourinew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniasouth-carolinatennesseetexasvirginiawest-virginia

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