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

Acadian Flycatcher Population Trend in Illinois

All statesAerial insectivores

Acadian Flycatcher in Illinois has surged: up 447% on the route-weighted index since 1968.

+447%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 →
62Routes 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 Acadian 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 →

Acadian Flycatcher has surged in Illinois: up 447% on the route-weighted index since 1968.

Acadian Flycatcher Population Forecast in Illinois

If the recent trend holds, Acadian Flycatcher in Illinois is projected to fall about 32% by 2029 — from 1.6 in 2024 to a central estimate of 1.1 (95% range 0.45–1.7). A 5-year backtest shows a typical error of ±46.7%, with 20% of held-out values landing inside the 95% band.

-32%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 →
1.1Projected 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 →
0.45–1.795% 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 →
±46.7%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, Acadian Flycatcher in Illinois is projected to fall about 32% by 2029 — from 1.6 in 2024 to a central estimate of 1.1 (95% range 0.45–1.7). A 5-year backtest shows a typical error of ±46.7%, with 20% 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 →
20251.00.401.7
20261.10.411.7
20271.10.421.7
20281.10.441.7
20291.10.451.7

Acadian Flycatcher Survey Routes in Illinois

Routes recording Acadian 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 →
Sandusky2220231993
Belleview2020241966
Bremen2020241969
Cave In Rock1820241993
York1320241993
Pulaski1220241970
Beaverdam Lk820231970
Delwood720241974
St Morgan520221967
Birds420241976
Belknap420241973
Chandlervill319721971
Bradbury320241983
Mascoutah Lk320241978
Marshall320242010
Guilford219991999
Payson220242006
Eubanks220242003
Athensville220221973
Pawnee219781967
Clarksdale220211968
Columbia220231966
Robinson220222021
Camp Point220232002
Royalton220242004

Acadian Flycatcher Population Trend in Other States

alabamaarkansasconnecticutdelawarefloridageorgiaindianaiowakansaskentuckylouisianamarylandmassachusettsmichiganminnesotamississippimissourinew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniarhode-islandsouth-carolinatennesseetexasvirginiawest-virginiawisconsin

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.