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

Blue-winged Warbler Population Trend in Illinois

All statesForest birds

Blue-winged Warbler in Illinois has increased: up 37% on the route-weighted index since 1979.

+37%Since 1979TrendPercent 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 →
22Routes 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 →
32YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Blue-winged 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 →

No notable trend signals for Blue-winged Warbler in Illinois. See the full index history below.

Blue-winged Warbler Population Forecast in Illinois

If the recent trend holds, Blue-winged Warbler in Illinois is projected to stay roughly flat through 2027, near 0.03 (95% range 0.00–0.06). A 5-year backtest shows a typical error of ±22.6%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2027TrendPercent 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 →
0.03Projected 2027 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.0695% 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 →
±22.6%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, Blue-winged Warbler in Illinois is projected to stay roughly flat through 2027, near 0.03 (95% range 0.00–0.06). A 5-year backtest shows a typical error of ±22.6%, with 100% of held-out values landing inside the 95% band.19712027
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 →
20230.030.000.06
20240.030.000.06
20250.030.000.06
20260.030.000.06
20270.030.000.06

Blue-winged Warbler Survey Routes in Illinois

Routes recording Blue-winged 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 →
New Lenox320072005
Concord219971997
Lake Galena220212021
Cherry Val120012001
Putnam119791979
Sheffield119961979
Newark119831983
Bartonville120222022
Dailey119851985
Bradbury120182018
Columbia119721971
Grape Creek120122012
Flora119951995
Marshall120182018
Bremen120221989
Delwood120171980
Beaverdam Lk119861986
Yale120022002
York119941994
Brownville120092009
Sandusky120181993
Cave In Rock120211994

Blue-winged Warbler Population Trend in Other States

alabamaarkansasconnecticutdelawaregeorgiaindianaiowakentuckymarylandmassachusettsmichiganminnesotamississippimissourinew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniarhode-islandtennesseevermontvirginiawest-virginiawisconsin

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