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

Field Sparrow Population Trend in Iowa

All statesGeneralists

Field Sparrow in Iowa has fallen sharply: down 52% on the route-weighted index since 1969.

-52%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 →
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 Field 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 →

Field Sparrow has fallen sharply in Iowa: down 52% on the route-weighted index since 1969.

Field Sparrow Population Forecast in Iowa

If the recent trend holds, Field Sparrow in Iowa is projected to rise about 35% by 2029 — from 2.4 in 2024 to a central estimate of 3.2 (95% range 1.1–5.4). A 5-year backtest shows a typical error of ±63.3%, with 100% of held-out values landing inside the 95% band.

+35%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 →
3.2Projected 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 →
1.1–5.495% 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 →
±63.3%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, Field Sparrow in Iowa is projected to rise about 35% by 2029 — from 2.4 in 2024 to a central estimate of 3.2 (95% range 1.1–5.4). A 5-year backtest shows a typical error of ±63.3%, 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 →
20253.31.25.4
20263.31.25.4
20273.31.15.4
20283.31.15.4
20293.21.15.4

Field Sparrow Survey Routes in Iowa

Routes recording Field 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 →
Washta2720141967
Mt Hamill1320241967
Bryant1220241967
Wales1020181967
Maquoketa820241967
Melrose720241974
Bedford620181968
Williamsburg620231967
Neola520161968
Pierson520191987
Festina520241968
Brooklyn420221967
Garner419921973
College Spgs 2420232005
West Liberty320241968
Alice319991967
Lafayette320192003
College Spgs220041967
Sioux City220191968
Davis Corner220241971
Exline120241974
Cedar Valley119971967
Red Rock120241968
Desmoines119791968
Panther120191973

Field Sparrow Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawarefloridageorgiaillinoisindianakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.