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Species · Illinois · BBS 2025 Release · 1966–2024

Carolina Chickadee Population Trend in Illinois

All statesForest birds

Carolina Chickadee in Illinois has surged: up 411% on the route-weighted index since 1968.

+411%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 →
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 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 411% 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 22% by 2029 — from 1.8 in 2024 to a central estimate of 1.4 (95% range 0.89–2.0). A 5-year backtest shows a typical error of ±29.1%, with 60% of held-out values landing inside the 95% band.

-22%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 →
1.4Projected 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 →
0.89–2.095% 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 →
±29.1%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 22% by 2029 — from 1.8 in 2024 to a central estimate of 1.4 (95% range 0.89–2.0). A 5-year backtest shows a typical error of ±29.1%, 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 →
20251.40.831.9
20261.40.841.9
20271.40.861.9
20281.40.881.9
20291.40.892.0

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 Vernon1420241971
Belknap1320241970
Bremen1220241969
Royalton1220242001
Bradbury1020241970
St Morgan1020221967
Pulaski1020241971
Birds820241976
Cave In Rock820241993
Grape Creek620242001
Mascoutah Lk620241978
Brnt Prairie620241977
Jamestown520231967
York520241993
Kell420242001
Brownville420241993
Janesville320241995
Beaverdam Lk320231970
Yale320241993
Beaucoup220241972
Olney220241966
Flora220191976
Delwood220241970
Robinson220231971
Marshall220242006

Carolina Chickadee Population Trend in Other States

alabamaarkansasdelawarefloridageorgiaindianakansaskentuckylouisianamarylandmississippimissourinew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniasouth-carolinatennesseetexasvirginiawest-virginia

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