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Species · Illinois · BBS 2026 Release · 1966–2025

Warbling Vireo Population Trend in Illinois

All statesForest birds

Warbling Vireo in Illinois has surged: up 175% on the route-weighted index since 1968.

+175%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 →
104Routes 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 Warbling Vireo 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 →

Warbling Vireo has surged in Illinois: up 175% on the route-weighted index since 1968.

Warbling Vireo Population Forecast in Illinois

If the recent trend holds, Warbling Vireo in Illinois is projected to stay roughly flat through 2030, near 5.0 (95% range 3.8–6.1). A 5-year backtest shows a typical error of ±14.4%, with 60% of held-out values landing inside the 95% band.

-6%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 →
5.0Projected 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 →
3.8–6.195% 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 →
±14.4%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, Warbling Vireo in Illinois is projected to stay roughly flat through 2030, near 5.0 (95% range 3.8–6.1). A 5-year backtest shows a typical error of ±14.4%, with 60% 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 →
20264.73.65.9
20274.83.65.9
20284.83.76.0
20294.93.86.0
20305.03.86.1

Warbling Vireo Survey Routes in Illinois

Routes recording Warbling Vireo 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 →
Belleview2620251966
Terre Haute1720251966
Guilford1620231967
Athensville1420251971
Geneseo1320251967
Bartonville1320251973
Concord1320251967
York1320251994
Payson1320252000
Bradbury1220251972
Dudleyville1220252001
Williamsfld1120251976
Union1020172005
Eubanks1020252001
Humboldt920251971
Jamestown920251966
Athens920251995
Sherburnvill820231976
Chandlervill820251971
Dailey820251971
Birds820241976
Janesville720251972
St Morgan720221967
Belknap720251972
Sherrard720251993

Warbling Vireo Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawareidahoindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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