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

Swainson's Warbler Population Trend in North Carolina

All statesForest birds

Swainson's Warbler in North Carolina has surged: up 860% on the route-weighted index since 1970.

+860%Since 1970TrendPercent 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 →
55Routes 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 →
56YearsYears 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 North 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 North Carolina: up 860% on the route-weighted index since 1970.

Swainson's Warbler Population Forecast in North Carolina

If the recent trend holds, Swainson's Warbler in North Carolina is projected to fall about 51% by 2030 — from 0.80 in 2025 to a central estimate of 0.39 (95% range 0.16–0.63). A 5-year backtest shows a typical error of ±38.5%, with 60% of held-out values landing inside the 95% band.

-51%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 →
0.39Projected 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 →
0.16–0.6395% 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 →
±38.5%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 North Carolina is projected to fall about 51% by 2030 — from 0.80 in 2025 to a central estimate of 0.39 (95% range 0.16–0.63). A 5-year backtest shows a typical error of ±38.5%, with 60% 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 →
20260.380.140.61
20270.380.150.62
20280.390.150.62
20290.390.160.63
20300.390.160.63

Swainson's Warbler Survey Routes in North Carolina

Routes recording Swainson's Warbler in North 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 →
Highlands1120251998
French Broad River720252001
Dismal Swamp520241996
Fontana520251977
Waterville420252022
Brevard320251986
Roseboro320251998
Raeford220251990
Sheep Ridge220251997
Table Rock220221994
Oakboro220252023
Chowan River220062002
Cullowhee220242022
Congleton220212004
Cypress Lakes220252017
Maple Hill220212001
Hendersonvil220252017
Murphy220241999
Oteen220232023
Shallotte119901970
Merrimon120231973
Myrtle Grove119861967
Wards Corner120101982
Hallsboro120131983
Fairmont119731973

Swainson's Warbler Population Trend in Other States

alabamaarkansasfloridageorgiakentuckylouisianamarylandmississippioklahomasouth-carolinatennesseetexasvirginiawest-virginia

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