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

Kentucky Warbler Population Trend in Illinois

All statesForest birds

Kentucky Warbler in Illinois has surged: up 206% on the route-weighted index since 1970.

+206%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 →
48Routes 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 →
57YearsYears 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 206% 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 15% by 2030 — from 0.53 in 2025 to a central estimate of 0.61 (95% range 0.39–0.83). A 5-year backtest shows a typical error of ±20.4%, with 80% of held-out values landing inside the 95% band.

+15%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 →
0.61Projected 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 →
0.39–0.8395% 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 →
±20.4%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 15% by 2030 — from 0.53 in 2025 to a central estimate of 0.61 (95% range 0.39–0.83). A 5-year backtest shows a typical error of ±20.4%, with 80% of held-out values landing inside the 95% band.19682030
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 →
20260.580.360.80
20270.590.370.81
20280.600.380.82
20290.600.390.82
20300.610.390.83

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
Delwood1220251970
Cave In Rock820241993
Bremen520251970
Belknap520251970
Beaverdam Lk420231970
Marshall420232011
Brownville420191999
Terre Haute219851980
Dailey220252005
Belleview220251969
Bradbury220251983
Mascoutah Lk220251979
Pulaski220251970
Royalton220192001
Karnak220252002
Yale220141997
Athens120252001
Payson120242005
Clayton120032003
Chandlervill120252025
Williamsfld120172017
Grape Creek120232002
Eubanks120252001
Melrose119921992

Kentucky Warbler Population Trend in Other States

alabamaarkansasdelawarefloridageorgiaindianaiowakansaskentuckylouisianamarylandmississippimissourinew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniasouth-carolinatennesseetexasvirginiawest-virginiawisconsin

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