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Species · Illinois · BBS 2025 Release · 1966–2024

Willow Flycatcher Population Trend in Illinois

All statesAerial insectivores

Willow Flycatcher in Illinois has held roughly steady: up 5% on the route-weighted index since 1968.

+5%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 →
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 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 stay roughly flat through 2029, near 0.46 (95% range 0.11–0.81). A 5-year backtest shows a typical error of ±25.5%, with 80% of held-out values landing inside the 95% band.

+7%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 →
0.46Projected 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 →
0.11–0.8195% 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 →
±25.5%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, Willow Flycatcher in Illinois is projected to stay roughly flat through 2029, near 0.46 (95% range 0.11–0.81). A 5-year backtest shows a typical error of ±25.5%, with 80% 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 →
20250.470.120.82
20260.470.120.81
20270.460.120.81
20280.460.110.81
20290.460.110.81

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 →
Clayton720232003
Belleview620231996
Alden520232019
Wayne420241967
Stillwell420231982
Robinson420231970
Darmstadt420232014
Putnam320241967
Flora320021996
Camp Point320231995
Mill Creek220231966
Cherry Val220031972
Buda220231989
Essex220162009
Gulfport220232001
Chandlervill220241973
Bartonville220241975
Deer Creek220241968
Mackinaw219871974
Fairbury220221999
Dailey220001986
Milford220121974
Bluff Spgs220231967
Athensville220241974
Concord220231967

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 2026-05-22.