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

Bell's Vireo Population Trend in South Dakota

All statesForest birds

Bell's Vireo in South Dakota has held roughly steady: down 3% on the route-weighted index since 1969.

-3%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 →
20Routes 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 →
47YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Bell's Vireo 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 →

No notable trend signals for Bell's Vireo in South Dakota. See the full index history below.

Bell's Vireo Population Forecast in South Dakota

If the recent trend holds, Bell's Vireo in South Dakota is projected to fall about 69% by 2030 — from 0.39 in 2025 to a central estimate of 0.12 (95% range 0.00–0.32). A 5-year backtest shows a typical error of ±43.8%, with 80% of held-out values landing inside the 95% band.

-69%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 →
0.12Projected 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 →
0.00–0.3295% 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 →
±43.8%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, Bell's Vireo in South Dakota is projected to fall about 69% by 2030 — from 0.39 in 2025 to a central estimate of 0.12 (95% range 0.00–0.32). A 5-year backtest shows a typical error of ±43.8%, with 80% 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 →
20260.120.000.32
20270.120.000.32
20280.120.000.32
20290.120.000.32
20300.120.000.32

Bell's Vireo Survey Routes in South Dakota

Routes recording Bell's Vireo 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 →
Rosebud720101973
Badlands520251990
Chamberlain420111967
Rockyford320251989
Lane319721967
Lacreek320251997
Winner220222005
Broadland219711971
Laplant219711971
Promise220151972
Tripp120182014
Geddes119961990
Crow Creek120162016
Ft Thompson120111968
Owanka119851984
Ottumwa119731973
Cedar Pass119751969
Fort Pierre120211968
Maurine120232023
White River120131994

Bell's Vireo Population Trend in Other States

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