BirdAnalyst
Species · South Dakota · BBS 2026 Release · 1966–2025

Swamp Sparrow Population Trend in South Dakota

All statesWetland birds

Swamp Sparrow in South Dakota has surged: up 167% on the route-weighted index since 1971.

+167%Since 1971TrendPercent 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 →
10Routes 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 →
40YearsYears 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 South DakotaNotable 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 →

Swamp Sparrow has surged in South Dakota: up 167% on the route-weighted index since 1971.

Swamp Sparrow Population Forecast in South Dakota

If the recent trend holds, Swamp Sparrow in South Dakota is projected to fall about 63% by 2030 — from 0.29 in 2025 to a central estimate of 0.11 (95% range 0.00–0.26). A 5-year backtest shows a typical error of ±76.4%, with 40% of held-out values landing inside the 95% band.

-63%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 →
0.11Projected 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 →
0.00–0.2695% 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 →
±76.4%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, Swamp Sparrow in South Dakota is projected to fall about 63% by 2030 — from 0.29 in 2025 to a central estimate of 0.11 (95% range 0.00–0.26). A 5-year backtest shows a typical error of ±76.4%, with 40% of held-out values landing inside the 95% band.19672030
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 →
20260.110.000.26
20270.110.000.26
20280.110.000.26
20290.110.000.26
20300.110.000.26

Swamp Sparrow Survey Routes in South Dakota

Routes recording Swamp Sparrow in South Dakota.
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 →
Wilmot520252017
Veblen320222006
Howard220191979
Lennox120251973
Volga120251967
Roswell119911971
Broadland120022000
Lacreek120232017
Britton119671967
Forbes120252004

Swamp Sparrow Population Trend in Other States

connecticutdelawareillinoisindianaiowamainemarylandmassachusettsmichiganminnesotanebraskanew-hampshirenew-jerseynew-yorknorth-dakotaohiopennsylvaniarhode-islandvermontvirginiawest-virginiawisconsin

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