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

Warbling Vireo Population Trend in Iowa

All statesForest birds

Warbling Vireo in Iowa has surged: up 209% on the route-weighted index since 1969.

+209%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 Warbling Vireo 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 →

Warbling Vireo has surged in Iowa: up 209% on the route-weighted index since 1969.

Warbling Vireo Population Forecast in Iowa

If the recent trend holds, Warbling Vireo in Iowa is projected to stay roughly flat through 2030, near 3.9 (95% range 2.9–5.0). A 5-year backtest shows a typical error of ±7.2%, with 100% of held-out values landing inside the 95% band.

+7%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 →
3.9Projected 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 →
2.9–5.095% 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 →
±7.2%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, Warbling Vireo in Iowa is projected to stay roughly flat through 2030, near 3.9 (95% range 2.9–5.0). A 5-year backtest shows a typical error of ±7.2%, 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 →
20263.72.74.8
20273.82.74.9
20283.82.84.9
20293.92.85.0
20303.92.95.0

Warbling Vireo Survey Routes in Iowa

Routes recording Warbling Vireo 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 →
Mt Hamill1620251967
Red Rock1020251968
Alice919991967
Festina920251968
Panther720251967
Sioux City720251969
West Liberty620251968
Pierson620251973
Maquoketa520251967
Washta520251968
Exline420251979
Melrose420251977
Bedford420251969
Bryant420251967
Mccallsburg420251996
Wales320251967
Brooklyn220251970
Washington220251967
Prairieburg220251974
Kanawha220251995
Zearing219951967
Clare220191967
Davis Corner220251978
Rock Valley220251970
College Spgs 2220252005

Warbling Vireo Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawareidahoillinoisindianakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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