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

Yellow Warbler Population Trend in Iowa

All statesForest birds

Yellow Warbler in Iowa has surged: up 229% on the route-weighted index since 1969.

+229%Since 1969TrendPercent 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 →
39Routes 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 Yellow Warbler 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 →

Yellow Warbler has surged in Iowa: up 229% on the route-weighted index since 1969.

Yellow Warbler Population Forecast in Iowa

If the recent trend holds, Yellow Warbler in Iowa is projected to fall about 16% by 2030 — from 1.5 in 2025 to a central estimate of 1.3 (95% range 0.74–1.8). A 5-year backtest shows a typical error of ±23.7%, with 100% of held-out values landing inside the 95% band.

-16%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 →
1.3Projected 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 →
0.74–1.895% 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 →
±23.7%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, Yellow Warbler in Iowa is projected to fall about 16% by 2030 — from 1.5 in 2025 to a central estimate of 1.3 (95% range 0.74–1.8). A 5-year backtest shows a typical error of ±23.7%, with 100% of held-out values landing inside the 95% band.19672030
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 →
20261.20.671.7
20271.20.691.7
20281.20.701.8
20291.20.721.8
20301.30.741.8

Yellow Warbler Survey Routes in Iowa

Routes recording Yellow Warbler 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 →
Red Rock520251969
Washta520251969
Mccallsburg420251996
Melrose320251994
Brooklyn320251973
Desmoines319791968
Davis Corner320231982
College Spgs 2320252005
Bryant220251967
West Liberty220251969
Maquoketa220241967
Prairieburg220251986
Clare220131975
Pierson220251973
Sioux City220251969
Festina220251968
Gaza220251973
Rock Valley220241970
Burchinal220241997
Lafayette220252012
Mt Hamill120191997
Exline120251981
Bedford120251971
College Spgs120031967
Cedar Valley119961970

Yellow Warbler Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianakansaskentuckymainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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