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Species · Illinois · BBS 2026 Release · 1966–2025

Great Crested Flycatcher Population Trend in Illinois

All statesAerial insectivores

Great Crested Flycatcher in Illinois has surged: up 146% on the route-weighted index since 1968.

+146%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 →
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 Great Crested 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 →

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 →

Great Crested Flycatcher has surged in Illinois: up 146% on the route-weighted index since 1968.

Great Crested Flycatcher Population Forecast in Illinois

If the recent trend holds, Great Crested Flycatcher in Illinois is projected to fall about 32% by 2030 — from 4.4 in 2025 to a central estimate of 3.0 (95% range 1.9–4.1). A 5-year backtest shows a typical error of ±35.6%, with 20% of held-out values landing inside the 95% band.

-32%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 →
3.0Projected 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 →
1.9–4.195% 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 →
±35.6%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, Great Crested Flycatcher in Illinois is projected to fall about 32% by 2030 — from 4.4 in 2025 to a central estimate of 3.0 (95% range 1.9–4.1). A 5-year backtest shows a typical error of ±35.6%, with 20% 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 →
20262.91.94.0
20273.01.94.0
20283.01.94.0
20293.01.94.1
20303.01.94.1

Great Crested Flycatcher Survey Routes in Illinois

Routes recording Great Crested 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 →
Bremen1820251969
Mascoutah Lk1720251970
Marshall1720252001
Bradbury1520251971
Eubanks1520252001
Beaverdam Lk1420231970
Athens1320251995
Belleview1220251966
Pulaski1120251970
Delwood1120251970
Royalton1020252003
Mt Vernon920251971
Payson920252000
Kell920252001
Terre Haute820251966
York820251993
Sandusky820231993
Monica720161973
Athensville720251971
St Morgan720221968
Eldred720251993
Yale720251994
Fairland620251978
Olney620241966
Robinson620231970

Great Crested Flycatcher Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawarefloridageorgiaindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsin

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