BirdAnalyst
Species · Illinois · BBS 2026 Release · 1966–2025

Wood Thrush Population Trend in Illinois

All statesForest birds

Wood Thrush in Illinois has surged: up 173% on the route-weighted index since 1968.

+173%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 →
100Routes 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 Wood Thrush 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 →

Wood Thrush has surged in Illinois: up 172% on the route-weighted index since 1968.

Wood Thrush Population Forecast in Illinois

If the recent trend holds, Wood Thrush in Illinois is projected to fall about 36% by 2030 — from 2.4 in 2025 to a central estimate of 1.5 (95% range 0.47–2.5). A 5-year backtest shows a typical error of ±59%, with 0% of held-out values landing inside the 95% band.

-36%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 →
1.5Projected 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 →
0.47–2.595% 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 →
±59%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, Wood Thrush in Illinois is projected to fall about 36% by 2030 — from 2.4 in 2025 to a central estimate of 1.5 (95% range 0.47–2.5). A 5-year backtest shows a typical error of ±59%, with 0% 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 →
20261.50.452.5
20271.50.462.5
20281.50.462.5
20291.50.472.5
20301.50.472.5

Wood Thrush Survey Routes in Illinois

Routes recording Wood Thrush 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 →
Delwood2620251970
York1920251995
Sandusky1620231993
Belleview1420251969
Bradbury820251971
Sheffield720241966
Chandlervill720251973
Bremen720251970
Royalton720252003
Grape Creek620252001
Marshall620252010
Deer Creek520241982
Concord520251976
Janesville520241977
Beaverdam Lk520231970
Robinson520231970
Guilford420231979
Stillwell420251976
Humboldt420221978
Shannon420241997
Camp Point420251993
Eldred420251994
Clayton420252010
Wayne320231966
Dailey320251969

Wood Thrush Population Trend in Other States

alabamaarkansasconnecticutdelawarefloridageorgiaindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsin

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