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Species · Iowa · BBS 2026 Release · 1966–2025

Henslow's Sparrow Population Trend in Iowa

All statesGrassland birds

Henslow's Sparrow in Iowa has surged: up 204% on the route-weighted index since 1978.

+204%Since 1978TrendPercent 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 →
16Routes 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 →
28YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Henslow's 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 →

No notable trend signals for Henslow's Sparrow in Iowa. See the full index history below.

Henslow's Sparrow Population Forecast in Iowa

If the recent trend holds, Henslow's Sparrow in Iowa is projected to rise about 254% by 2030 — from 0.07 in 2025 to a central estimate of 0.23 (95% range 0.00–0.60). A 5-year backtest shows a typical error of ±220%, with 100% of held-out values landing inside the 95% band.

+254%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 →
0.23Projected 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 →
0.00–0.6095% 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 →
±220%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, Henslow's Sparrow in Iowa is projected to rise about 254% by 2030 — from 0.07 in 2025 to a central estimate of 0.23 (95% range 0.00–0.60). A 5-year backtest shows a typical error of ±220%, with 100% of held-out values landing inside the 95% band.19742030
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 →
20260.220.000.59
20270.220.000.59
20280.230.000.60
20290.230.000.60
20300.230.000.60

Henslow's Sparrow Survey Routes in Iowa

Routes recording Henslow's 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 →
Williamsburg420082003
Bedford220132001
Bryant220252022
West Liberty220172009
College Spgs 2220082008
Mt Hamill120121981
Exline120082000
Melrose120071984
Gaza120092009
Brooklyn120222003
Wales120182018
Maquoketa120242017
Hudson119781978
Zearing119741974
Festina120232023
Davis Corner119771977

Henslow's Sparrow Population Trend in Other States

delawareillinoisindianakansaskentuckymarylandmichiganminnesotamissourinebraskanew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniasouth-dakotavermontvirginiawest-virginiawisconsin

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