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Species · Illinois · BBS 2025 Release · 1966–2024

Kentucky Warbler Population Trend in Illinois

All statesForest birds

Kentucky Warbler in Illinois has surged: up 224% on the route-weighted index since 1970.

+224%Since 1970TrendPercent 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 →
47Routes 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 →
56YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Kentucky Warbler 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 →

Kentucky Warbler has surged in Illinois: up 224% on the route-weighted index since 1970.

Kentucky Warbler Population Forecast in Illinois

If the recent trend holds, Kentucky Warbler in Illinois is projected to rise about 38% by 2029 — from 0.44 in 2024 to a central estimate of 0.61 (95% range 0.39–0.83). A 5-year backtest shows a typical error of ±22.7%, with 80% of held-out values landing inside the 95% band.

+38%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 →
0.61Projected 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 →
0.39–0.8395% 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 →
±22.7%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, Kentucky Warbler in Illinois is projected to rise about 38% by 2029 — from 0.44 in 2024 to a central estimate of 0.61 (95% range 0.39–0.83). A 5-year backtest shows a typical error of ±22.7%, with 80% of held-out values landing inside the 95% band.19682029
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 →
20250.580.360.80
20260.590.360.81
20270.590.370.81
20280.600.380.82
20290.610.390.83

Kentucky Warbler Survey Routes in Illinois

Routes recording Kentucky Warbler 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 →
Sandusky1320231993
Cave In Rock820241993
Pulaski620241970
Delwood620241970
Belknap420241970
Beaverdam Lk420231970
Marshall420232011
Brownville420191999
Bremen320241970
York320231994
Terre Haute219851980
Eubanks220182001
Belleview220241969
Dudleyville220222006
Royalton220192001
Karnak220242002
Yale220141997
Athens120182001
Payson120242005
Clayton120032003
Williamsfld120172017
Grape Creek120232002
Dailey120172005
Melrose119921992
Bluff Spgs119731973

Kentucky Warbler Population Trend in Other States

alabamaarkansasdelawarefloridageorgiaindianaiowakansaskentuckylouisianamarylandmississippimissourinew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniasouth-carolinatennesseetexasvirginiawest-virginiawisconsin

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