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Species · Illinois · BBS 2026 Release · 1966–2025

Yellow Warbler Population Trend in Illinois

All statesForest birds

Yellow Warbler in Illinois has surged: up 169% on the route-weighted index since 1968.

+169%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 →
101Routes 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 Yellow 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 →

Yellow Warbler has surged in Illinois: up 169% on the route-weighted index since 1968.

Yellow Warbler Population Forecast in Illinois

If the recent trend holds, Yellow Warbler in Illinois is projected to fall about 35% by 2030 — from 1.6 in 2025 to a central estimate of 1.0 (95% range 0.62–1.4). A 5-year backtest shows a typical error of ±16.5%, with 80% of held-out values landing inside the 95% band.

-35%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 →
1.0Projected 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 →
0.62–1.495% 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 →
±16.5%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, Yellow Warbler in Illinois is projected to fall about 35% by 2030 — from 1.6 in 2025 to a central estimate of 1.0 (95% range 0.62–1.4). A 5-year backtest shows a typical error of ±16.5%, with 80% 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 →
20260.980.591.4
20270.990.591.4
20281.00.601.4
20291.00.611.4
20301.00.621.4

Yellow Warbler Survey Routes in Illinois

Routes recording Yellow 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 →
Belleview1920251979
Union1020172001
Lake Galena820212001
Bartonville620251985
Bradbury620251972
Sherrard620251994
Marshall620252010
Humboldt520251981
Birds520241977
Eldred520252000
York520251996
Wayne420251968
Newark420221970
Jamestown420251968
Shannon420231993
Mill Creek320251970
Barrington320111970
Sherburnvill320231967
Dailey320251976
Seneca320251997
Grape Creek320252001
Concord West320252001
Cherry Val220031973
Putnam220241967
Sheffield220221967

Yellow Warbler Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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