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

Yellow Warbler Population Trend in Illinois

All statesForest birds

Yellow Warbler in Illinois has surged: up 114% on the route-weighted index since 1968.

+114%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 →
98Routes 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 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 114% 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 rise about 19% by 2029 — from 0.81 in 2024 to a central estimate of 0.96 (95% range 0.59–1.3). A 5-year backtest shows a typical error of ±8.8%, with 100% 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 →
0.96Projected 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 →
0.59–1.395% 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 →
±8.8%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 rise about 19% by 2029 — from 0.81 in 2024 to a central estimate of 0.96 (95% range 0.59–1.3). A 5-year backtest shows a typical error of ±8.8%, with 100% 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 →
20250.930.561.3
20260.940.571.3
20270.950.581.3
20280.960.591.3
20290.960.591.3

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 →
Belleview1520241979
Union1020172001
Lake Galena820212001
Alden720232019
Birds520241977
Newark420221970
Shannon420231993
Marshall420242010
Barrington320111970
Sherburnvill320231967
Bartonville320241985
Sherrard320241994
Lake Summerset320222001
Grape Creek320242001
Concord West320232001
Cherry Val220031973
Putnam220241967
Sheffield220221967
Wayne220241968
Cameron220242017
Deer Creek220241968
Bluff Spgs220211970
St Morgan220021972
Beaucoup220221994
Flora219981978

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 2026-05-22.