BirdAnalyst
Species · North Carolina · BBS 2025 Release · 1966–2024

Swainson's Warbler Population Trend in North Carolina

All statesForest birds

Swainson's Warbler in North Carolina has surged: up 624% on the route-weighted index since 1970.

+624%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 →
55YearsYears 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 624% 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 39% by 2029 — from 0.59 in 2024 to a central estimate of 0.35 (95% range 0.15–0.56). A 5-year backtest shows a typical error of ±28%, with 80% of held-out values landing inside the 95% band.

-39%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 →
0.35Projected 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 →
0.15–0.5695% 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 →
±28%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 39% by 2029 — from 0.59 in 2024 to a central estimate of 0.35 (95% range 0.15–0.56). A 5-year backtest shows a typical error of ±28%, with 80% 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 →
20250.340.140.55
20260.350.140.55
20270.350.140.55
20280.350.150.56
20290.350.150.56

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 →
Fontana720241977
Highlands620241998
Dismal Swamp520241996
Sheep Ridge320241997
Brevard320241986
Waterville220222022
Table Rock220221994
Chowan River220062002
Cullowhee220242022
French Broad River220242001
Congleton220212004
Maple Hill220212001
Roseboro220241998
Murphy220241999
Oteen220232023
Shallotte119901970
Merrimon120231973
Myrtle Grove119861967
Wards Corner120101982
Hallsboro120131983
Fairmont119731973
Raeford119991990
Arapahoe119931980
Speed120231978
Kinston120221995

Swainson's Warbler Population Trend in Other States

alabamaarkansasfloridageorgiakentuckylouisianamarylandmississippioklahomasouth-carolinatennesseetexasvirginiawest-virginia

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