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Species · South Carolina · BBS 2025 Release · 1966–2024

Swainson's Warbler Population Trend in South Carolina

All statesForest birds

Swainson's Warbler in South Carolina has surged: up 91% on the route-weighted index since 1976.

+91%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 →
24Routes 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 →
34YearsYears 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 91% 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 36% by 2029 — from 0.24 in 2024 to a central estimate of 0.15 (95% range 0.02–0.28). A 5-year backtest shows a typical error of ±65.5%, with 80% of held-out values landing inside the 95% band.

-36%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 →
0.15Projected 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 →
0.02–0.2895% 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 →
±65.5%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, Swainson's Warbler in South Carolina is projected to fall about 36% by 2029 — from 0.24 in 2024 to a central estimate of 0.15 (95% range 0.02–0.28). A 5-year backtest shows a typical error of ±65.5%, with 80% of held-out values landing inside the 95% band.19732029
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 →
20250.150.010.28
20260.150.020.28
20270.150.020.28
20280.150.020.28
20290.150.020.28

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 →
Jamestown220052000
Wagener220242024
Plum Branch219881988
Green Sea220242021
Dale220152006
Hardeeville120192019
Rome120232007
Holly Hill120242001
Foreston119751975
New Holland119791973
Dillon120081999
Walterboro120091976
Ward120172017
Whitmire120222022
Greenwood120102009
Mount Pisgah120192014
Bennettsville120102010
Olar120071998
Carvers Bay120101998
Nixville120082008
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 2026-05-22.