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

Great Crested Flycatcher Population Trend in Illinois

All statesAerial insectivores

Great Crested Flycatcher in Illinois has surged: up 122% on the route-weighted index since 1968.

+122%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 →
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 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 122% 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 19% by 2029 — from 3.5 in 2024 to a central estimate of 2.9 (95% range 1.9–3.9). A 5-year backtest shows a typical error of ±28.6%, with 40% 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 →
2.9Projected 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 →
1.9–3.995% 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 →
±28.6%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 19% by 2029 — from 3.5 in 2024 to a central estimate of 2.9 (95% range 1.9–3.9). A 5-year backtest shows a typical error of ±28.6%, with 40% 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 →
20252.81.83.8
20262.81.83.8
20272.81.83.8
20282.91.83.9
20292.91.93.9

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 →
Bremen2320241969
Belknap2120241970
Royalton2020242003
Belleview1820241966
York1520241993
Beaverdam Lk1420231970
Eubanks1220242001
Mascoutah Lk1020241970
Pulaski1020241970
Payson1020242000
Sandusky820231993
Marshall820242001
Terre Haute720241966
Monica720161973
St Morgan720221968
Janesville620231979
Bradbury620241971
Olney620241966
Robinson620231970
Alden620232019
Allerton Park620232003
Mill Creek520241967
Buda520221977
Stillwell520231971
Bartonville520241973

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 2026-05-22.