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Species · Illinois · BBS 2025 Release · 1966–2024

Warbling Vireo Population Trend in Illinois

All statesForest birds

Warbling Vireo in Illinois has surged: up 155% on the route-weighted index since 1968.

+155%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 →
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 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 155% 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 rise about 19% by 2029 — from 4.1 in 2024 to a central estimate of 4.8 (95% range 3.7–6.0). A 5-year backtest shows a typical error of ±13.5%, with 60% of held-out values landing inside the 95% band.

+19%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 →
4.8Projected 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 →
3.7–6.095% 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 →
±13.5%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 rise about 19% by 2029 — from 4.1 in 2024 to a central estimate of 4.8 (95% range 3.7–6.0). A 5-year backtest shows a typical error of ±13.5%, 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 →
20254.63.55.8
20264.73.55.8
20274.73.65.9
20284.83.65.9
20294.83.76.0

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 →
Belleview3420241966
Guilford1620231967
Duncan Mills1220241993
Eldred1220211993
Chandlervill1120241971
Mackinaw1120241967
Brownville1120191993
York1020241994
Payson1020242000
Union1020172005
Bartonville920241973
Alden920232019
Eubanks920242001
Sherburnvill820231976
Terre Haute820241966
Williamsfld820241976
Birds820241976
Greenview820231995
Concord720241967
Martinsville720241976
St Morgan720221967
Clayton720242001
Wayne620241967
Janesville620241972
Bradbury620241972

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 2026-05-22.