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Species · South Carolina · BBS 2026 Release · 1966–2025

Swainson's Warbler Population Trend in South Carolina

All statesForest birds

Swainson's Warbler in South Carolina has surged: up 187% on the route-weighted index since 1976.

+187%Since 1976TrendPercent 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 →
25Routes 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 →
35YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Swainson's Warbler Trends in South CarolinaNotable 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 →

Swainson's Warbler has surged in South Carolina: up 187% on the route-weighted index since 1976.

Swainson's Warbler Population Forecast in South Carolina

If the recent trend holds, Swainson's Warbler in South Carolina is projected to fall about 64% by 2030 — from 0.54 in 2025 to a central estimate of 0.19 (95% range 0.01–0.38). A 5-year backtest shows a typical error of ±77.3%, with 60% of held-out values landing inside the 95% band.

-64%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 →
0.19Projected 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 →
0.01–0.3895% 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 →
±77.3%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, Swainson's Warbler in South Carolina is projected to fall about 64% by 2030 — from 0.54 in 2025 to a central estimate of 0.19 (95% range 0.01–0.38). A 5-year backtest shows a typical error of ±77.3%, with 60% of held-out values landing inside the 95% band.19732030
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 →
20260.180.000.36
20270.190.010.37
20280.190.010.37
20290.190.010.37
20300.190.010.38

Swainson's Warbler Survey Routes in South Carolina

Routes recording Swainson's Warbler in South Carolina.
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 →
Green Sea420252021
Rome320252007
Jamestown220052000
New Holland220251973
Plum Branch219881988
Hardeeville120192019
Holly Hill120252001
Foreston119751975
Wagener120252024
Dillon120081999
Walterboro120251976
Ward120252017
Whitmire120222022
Greenwood120102009
Joanna120252025
Mount Pisgah120192014
Bennettsville120102010
Olar120071998
Carvers Bay120101998
Nixville120082008
Dale120252006
Battlecreek120082008
Adams Run120172004
Cauthens Xrd119851985
Prosperity120171992

Swainson's Warbler Population Trend in Other States

alabamaarkansasfloridageorgiakentuckylouisianamarylandmississippinorth-carolinaoklahomatennesseetexasvirginiawest-virginia

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