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

Prairie Warbler Population Trend in Illinois

All statesForest birds

Prairie Warbler in Illinois has surged: up 194% on the route-weighted index since 1973.

+194%Since 1973TrendPercent 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 →
22Routes 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 →
53YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Prairie Warbler 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 →

Prairie Warbler has surged in Illinois: up 194% on the route-weighted index since 1973.

Prairie Warbler Population Forecast in Illinois

If the recent trend holds, Prairie Warbler in Illinois is projected to fall about 36% by 2029 — from 0.25 in 2024 to a central estimate of 0.16 (95% range 0.01–0.32). A 5-year backtest shows a typical error of ±61.4%, with 20% of held-out values landing inside the 95% band.

-36%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 →
0.16Projected 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 →
0.01–0.3295% 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 →
±61.4%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, Prairie Warbler in Illinois is projected to fall about 36% by 2029 — from 0.25 in 2024 to a central estimate of 0.16 (95% range 0.01–0.32). A 5-year backtest shows a typical error of ±61.4%, with 20% of held-out values landing inside the 95% band.19712029
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 →
20250.160.000.31
20260.160.000.31
20270.160.000.32
20280.160.000.32
20290.160.010.32

Prairie Warbler Survey Routes in Illinois

Routes recording Prairie Warbler 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 →
Delwood620241972
Belknap520241971
Belleview420242016
Beaverdam Lk320231974
Robinson320222021
Camp Point219971997
Cave In Rock220241993
Dailey120002000
Milford119921992
Clarksdale120232023
Brnt Prairie119761976
Mt Vernon120142014
Eubanks120242010
Birds120232023
Pulaski120031971
Bremen120221972
Royalton120142014
Karnak120232012
Nilwood120012001
York120242024
Brownville120232015
Sandusky120221997

Prairie Warbler Population Trend in Other States

alabamaarkansascaliforniaconnecticutdelawarefloridageorgiaindianakentuckylouisianamainemarylandmassachusettsmichiganmississippimissourinew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniarhode-islandsouth-carolinatennesseetexasvermontvirginiawest-virginiawisconsin

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