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

Swamp Sparrow Population Trend in Iowa

All statesWetland birds

Swamp Sparrow in Iowa has declined: down 41% on the route-weighted index since 1974.

-41%Since 1974TrendPercent 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 →
14Routes 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 Swamp 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 Swamp Sparrow in Iowa. See the full index history below.

Swamp Sparrow Population Forecast in Iowa

If the recent trend holds, Swamp Sparrow in Iowa is projected to fall about 46% by 2030 — from 0.10 in 2025 to a central estimate of 0.05 (95% range 0.00–0.14). A 5-year backtest shows a typical error of ±62.2%, with 100% of held-out values landing inside the 95% band.

-46%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 →
0.05Projected 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 →
0.00–0.1495% 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 →
±62.2%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, Swamp Sparrow in Iowa is projected to fall about 46% by 2030 — from 0.10 in 2025 to a central estimate of 0.05 (95% range 0.00–0.14). A 5-year backtest shows a typical error of ±62.2%, with 100% of held-out values landing inside the 95% band.19712030
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 →
20260.060.000.14
20270.050.000.14
20280.050.000.14
20290.050.000.14
20300.050.000.14

Swamp Sparrow Survey Routes in Iowa

Routes recording Swamp 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 →
Scranton320031978
Titonka120251983
Rock Valley120192019
Burchinal120252003
Bryant120252013
Cedar Valley119831983
Williamsburg119971993
Prairieburg119921990
Hudson119821982
Kanawha120241973
Zearing119771977
Clare119761976
Davis Corner119891977
Garner119931971

Swamp Sparrow Population Trend in Other States

connecticutdelawareillinoisindianamainemarylandmassachusettsmichiganminnesotanebraskanew-hampshirenew-jerseynew-yorknorth-dakotaohiopennsylvaniarhode-islandsouth-dakotavermontvirginiawest-virginiawisconsin

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