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Species · Illinois · BBS 2026 Release · 1966–2025

Willow Flycatcher Population Trend in Illinois

All statesAerial insectivores

Willow Flycatcher in Illinois has held roughly steady: up 9% on the route-weighted index since 1968.

+9%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 →
99Routes 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 Willow Flycatcher 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 Willow Flycatcher in Illinois. See the full index history below.

Willow Flycatcher Population Forecast in Illinois

If the recent trend holds, Willow Flycatcher in Illinois is projected to fall about 24% by 2030 — from 0.61 in 2025 to a central estimate of 0.47 (95% range 0.12–0.81). A 5-year backtest shows a typical error of ±32.4%, with 80% of held-out values landing inside the 95% band.

-24%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 →
0.47Projected 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 →
0.12–0.8195% 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 →
±32.4%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, Willow Flycatcher in Illinois is projected to fall about 24% by 2030 — from 0.61 in 2025 to a central estimate of 0.47 (95% range 0.12–0.81). A 5-year backtest shows a typical error of ±32.4%, 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 →
20260.480.130.82
20270.470.130.82
20280.470.120.82
20290.470.120.82
20300.470.120.81

Willow Flycatcher Survey Routes in Illinois

Routes recording Willow Flycatcher 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 →
Greenview520251993
Alden520232019
Robinson420231970
Darmstadt420232014
Putnam320241967
Flora320021996
Eldred320252002
Grape Creek320252003
Mill Creek220231966
Cherry Val220031972
Buda220231989
Gulfport220232001
Cameron220251972
Deer Creek220241968
Mackinaw219871974
Milford220121974
Bluff Spgs220251967
Belleview220251996
Pawnee220251969
Bradbury220231984
Beaucoup220251974
Delwood219971983
Troy Grove220221995
Union220172006
Clayton220252003

Willow Flycatcher Population Trend in Other States

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

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