BirdAnalyst
Species · South Dakota · BBS 2025 Release · 1966–2024

Purple Martin Population Trend in South Dakota

All statesAerial insectivores

Purple Martin in South Dakota 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 →
13Routes 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 →
49YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Purple Martin 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 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 →

Purple Martin has fallen sharply in South Dakota: down 52% on the route-weighted index since 1969.

Purple Martin Population Forecast in South Dakota

If the recent trend holds, Purple Martin in South Dakota is projected to fall about 92% by 2029 — from 0.41 in 2024 to a central estimate of 0.03 (95% range 0.00–0.46). A 5-year backtest shows a typical error of ±72.5%, with 100% of held-out values landing inside the 95% band.

-92%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 →
0.03Projected 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 →
0.00–0.4695% 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 →
±72.5%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, Purple Martin in South Dakota is projected to fall about 92% by 2029 — from 0.41 in 2024 to a central estimate of 0.03 (95% range 0.00–0.46). A 5-year backtest shows a typical error of ±72.5%, 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 →
20250.060.000.49
20260.050.000.48
20270.050.000.48
20280.040.000.47
20290.030.000.46

Purple Martin Survey Routes in South Dakota

Routes recording Purple Martin 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 →
Tripp1519881986
Broadland1019691969
Lennox820241967
Geddes419701970
Roswell219791976
Veblen220231971
Forbes219861986
Howard119801980
White Lake120002000
Volga120241967
Wilmot119831967
Britton119761967
Long Lake119821982

Purple Martin Population Trend in Other States

alabamaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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