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

Wood Thrush Population Trend in Illinois

All statesForest birds

Wood Thrush in Illinois has surged: up 183% on the route-weighted index since 1968.

+183%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 →
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 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 183% 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 2029 — from 2.2 in 2024 to a central estimate of 1.4 (95% range 0.42–2.4). A 5-year backtest shows a typical error of ±58.8%, with 0% 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 →
1.4Projected 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 →
0.42–2.495% 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 →
±58.8%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 2029 — from 2.2 in 2024 to a central estimate of 1.4 (95% range 0.42–2.4). A 5-year backtest shows a typical error of ±58.8%, with 0% 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 →
20251.40.402.4
20261.40.402.4
20271.40.412.4
20281.40.412.4
20291.40.422.4

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 →
Delwood2920241970
Sandusky1620231993
Belknap1520241970
Royalton1320242003
Belleview1220241969
Eldred1020211994
Duncan Mills820242007
Sheffield720241966
Concord720241976
Deer Creek520241982
Mackinaw520221981
Janesville520241977
Beaverdam Lk520231970
Robinson520231970
York520241995
Guilford420231979
Stillwell420241976
Chandlervill420241973
Humboldt420221978
Bremen420241970
Shannon420241997
Marshall420242010
Wayne320231966
Pawnee320231967
Bradbury320241971

Wood Thrush Population Trend in Other States

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

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