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

Wood Thrush Population Trend in Iowa

All statesForest birds

Wood Thrush in Iowa has surged: up 468% on the route-weighted index since 1973.

+468%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 →
23Routes 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 →
46YearsYears 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 IowaNotable 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 Iowa: up 468% on the route-weighted index since 1973.

Wood Thrush Population Forecast in Iowa

If the recent trend holds, Wood Thrush in Iowa is projected to fall about 44% by 2029 — from 0.32 in 2024 to a central estimate of 0.18 (95% range 0.05–0.31). A 5-year backtest shows a typical error of ±81.7%, with 40% of held-out values landing inside the 95% band.

-44%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 →
0.18Projected 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 →
0.05–0.3195% 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 →
±81.7%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, Wood Thrush in Iowa is projected to fall about 44% by 2029 — from 0.32 in 2024 to a central estimate of 0.18 (95% range 0.05–0.31). A 5-year backtest shows a typical error of ±81.7%, with 40% of held-out values landing inside the 95% band.19702029
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 →
20250.170.040.30
20260.170.040.30
20270.170.040.30
20280.180.040.31
20290.180.050.31

Wood Thrush Survey Routes in Iowa

Routes recording Wood Thrush in Iowa.
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 →
Bedford419921992
Lafayette320182007
Mt Hamill220241973
Panther220142001
Wales220181973
Maquoketa220241989
Alice219991970
Exline120171976
Melrose120242022
Burchinal120032003
Bryant120231995
West Liberty120231972
Cedar Valley119921982
Red Rock120241974
Washington120041988
Prairieburg119991993
Clare120191999
Pierson120132013
Washta120101980
Festina119981978
Davis Corner119871987
Rock Valley119801980
Tipton120241993

Wood Thrush Population Trend in Other States

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

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