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

Vesper Sparrow Population Trend in Iowa

All statesGrassland birds

Vesper Sparrow in Iowa has fallen sharply: down 66% on the route-weighted index since 1969.

-66%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 →
38Routes 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 Vesper Sparrow 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 declinecomputed 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 →

Vesper Sparrow has fallen sharply in Iowa: down 66% on the route-weighted index since 1969.

Vesper Sparrow Population Forecast in Iowa

If the recent trend holds, Vesper Sparrow in Iowa is projected to stay roughly flat through 2030, near 6.2 (95% range 0.00–16). A 5-year backtest shows a typical error of ±34.9%, 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 →
6.2Projected 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 →
0.00–1695% 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 →
±34.9%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, Vesper Sparrow in Iowa is projected to stay roughly flat through 2030, near 6.2 (95% range 0.00–16). A 5-year backtest shows a typical error of ±34.9%, 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 →
20267.00.0017
20276.80.0016
20286.60.0016
20296.40.0016
20306.20.0016

Vesper Sparrow Survey Routes in Iowa

Routes recording Vesper Sparrow 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 →
Cedar Valley4619971967
Mccallsburg3320251996
Titonka3220251968
Kanawha3120251967
Prairieburg2720001967
Panther1920251967
Clare1620191967
Burchinal1120251995
Hudson820251967
Pierson820251968
Garner819931971
Gaza820251969
Desmoines719741968
Rock Valley720251968
West Liberty620191968
Neola519881968
Dinsdale520251968
Zearing519951968
Scranton420251967
College Spgs319911979
Wales320251967
Brooklyn220251967
Washington220251967
Maquoketa220221967
Alice219971968

Vesper Sparrow Population Trend in Other States

arizonacaliforniacoloradoconnecticutdelawareidahoillinoisindianakansaskentuckymainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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