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

Swamp Sparrow Population Trend in Iowa

All statesGeneralists

Swamp Sparrow in Iowa has fallen sharply: down 59% on the route-weighted index since 1974.

-59%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 →
26YearsYears 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 →

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 →

Swamp Sparrow has fallen sharply in Iowa: down 59% on the route-weighted index since 1974.

Swamp Sparrow Population Forecast in Iowa

If the recent trend holds, Swamp Sparrow in Iowa is projected to stay roughly flat through 2029, near 0.04 (95% range 0.00–0.13). A 5-year backtest shows a typical error of ±53.6%, with 80% of held-out values landing inside the 95% band.

n/aChange 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 →
0.04Projected 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 →
0.00–0.1395% 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 →
±53.6%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 stay roughly flat through 2029, near 0.04 (95% range 0.00–0.13). A 5-year backtest shows a typical error of ±53.6%, with 80% of held-out values landing inside the 95% band.19712029
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 →
20250.040.000.14
20260.040.000.14
20270.040.000.13
20280.040.000.13
20290.040.000.13

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
Burchinal220032003
Titonka119831983
Rock Valley120192019
Bryant120132013
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 2026-05-22.