BirdAnalyst
Species · BBS 2026 Release · 1966–2025

Swainson's Warbler Population Analysis

ParulidaeForest birdsLimnothlypis swainsonii

Swainson's Warbler has surged: up 39× on the route-weighted index since 1968.

39×Since 1968TrendPercent 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 →
422RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
59Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

About the Swainson's Warbler

The Swainson's Warbler (Limnothlypis swainsonii) is a North American member of the Wood-Warblers (Parulidae). In this analysis it is grouped with the forest birds.

Size
4.5–5.5 in long (11–14 cm) — a small, active songbird (typical for the family)
Habitat
Woodlands and forest edges, including wooded suburbs and parks.
Diet
Insects and spiders gleaned from foliage and bark, with seeds and berries in season.
Range
Recorded on 422 Breeding Bird Survey routes across 15 states, most concentrated in the Southeastern Coastal Plain.
Family
Parulidae · Forest birds

Notable Swainson's Warbler TrendsNotable 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 Swainson's Warbler. See the full index history below.

Swainson's Warbler Population Forecast

If the recent trend holds, Swainson's Warbler is projected to fall about 36% by 2030 — from 0.14 in 2025 to a central estimate of 0.09 (95% range 0.06–0.12). A 5-year backtest shows a typical error of ±40.5%, with 0% of held-out values landing inside the 95% band.

-36%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 →
0.09Projected 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 →
0.06–0.1295% 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 →
±40.5%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 is projected to fall about 36% by 2030 — from 0.14 in 2025 to a central estimate of 0.09 (95% range 0.06–0.12). A 5-year backtest shows a typical error of ±40.5%, with 0% of held-out values landing inside the 95% band.19662030
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 →
20260.080.060.11
20270.080.060.11
20280.090.060.11
20290.090.060.11
20300.090.060.12

Where the Swainson's Warbler Is Detected

BBS routes recording Swainson's Warbler, sized by most recent count.

Swainson's Warbler Population Trend by State

Swainson's Warbler population trend by state.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Alabama32×197077
Arkansas+158%197015
Florida+160%197325
Georgia+572%197557
Kentucky+15%198110
Louisiana+520%197450
Marylandinsufficient datan/a1
Mississippi+53%197434
North Carolina+860%197055
Oklahomainsufficient datan/a1
South Carolina+187%197625
Tennessee21×197216
Texas+278%197430
Virginia+203%197511
West Virginia+310%197515

Swainson's Warbler Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Swainson's Warbler population trend by Bird Conservation Region.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Oaks and Prairies+227%19997
West Gulf Coastal Plain / Ouachitas+729%197066
Mississippi Alluvial Valley+113%197718
Southeastern Coastal Plain34×1968220
Appalachian Mountains23×197170
Piedmont+565%198132

Swainson's Warbler Conservation Status

Our route-weighted index shows it up about 3754% since 1968.

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14. Trend is a route-weighted relative-abundance index, not an absolute population.