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

Yellow Warbler Population Trend in Iowa

All statesForest birds

Yellow Warbler in Iowa has surged: up 201% on the route-weighted index since 1969.

+201%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 →
57YearsYears 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 201% 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 2029 — from 1.5 in 2024 to a central estimate of 1.2 (95% range 0.70–1.7). A 5-year backtest shows a typical error of ±22.9%, with 100% of held-out values landing inside the 95% band.

-16%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 →
1.2Projected 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 →
0.70–1.795% 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 →
±22.9%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 2029 — from 1.5 in 2024 to a central estimate of 1.2 (95% range 0.70–1.7). A 5-year backtest shows a typical error of ±22.9%, with 100% of held-out values landing inside the 95% band.19672029
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 →
20251.20.631.7
20261.20.651.7
20271.20.671.7
20281.20.681.7
20291.20.701.7

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 →
Sioux City920241969
College Spgs 2720232005
Bryant420241967
Washta420141969
West Liberty320241969
Desmoines319791968
Davis Corner320231982
Mccallsburg320241996
Brooklyn220191973
Wales220181967
Maquoketa220241967
Clare220131975
Pierson220131973
Rock Valley220241970
Burchinal220241997
Mt Hamill120191997
Exline120241981
Melrose120241994
Bedford120161971
College Spgs120031967
Cedar Valley119961970
Williamsburg120231977
Red Rock120231969
Panther120241973
Washington120241967

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 2026-05-22.