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

Henslow's Sparrow Population Trend in Iowa

All statesGrassland birds

Henslow's Sparrow in Iowa has surged: up 293% on the route-weighted index since 1978.

+293%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 →
27YearsYears 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 →

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 →

Henslow's Sparrow has surged in Iowa: up 293% on the route-weighted index since 1978.

Henslow's Sparrow Population Forecast in Iowa

If the recent trend holds, Henslow's Sparrow in Iowa is projected to rise about 173% by 2029 — from 0.09 in 2024 to a central estimate of 0.25 (95% range 0.00–0.62). A 5-year backtest shows a typical error of ±308.4%, with 100% of held-out values landing inside the 95% band.

+173%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 →
0.25Projected 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 →
0.00–0.6295% 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 →
±308.4%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 173% by 2029 — from 0.09 in 2024 to a central estimate of 0.25 (95% range 0.00–0.62). A 5-year backtest shows a typical error of ±308.4%, with 100% of held-out values landing inside the 95% band.19742029
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 →
20250.240.000.61
20260.240.000.61
20270.240.000.62
20280.240.000.62
20290.250.000.62

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
West Liberty220172009
College Spgs 2220082008
Mt Hamill120121981
Exline120082000
Melrose120071984
Gaza120092009
Bryant120242022
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 2026-05-22.