BirdAnalyst
Species · BBS 2026 Release · 1966–2025

Black-throated Blue Warbler Population Analysis

ParulidaeForest birdsSetophaga caerulescens

Black-throated Blue Warbler has surged: up 105% on the route-weighted index since 1968.

+105%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 →
489RoutesSurvey 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 Black-throated Blue Warbler

The Black-throated Blue Warbler (Setophaga caerulescens) 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 489 Breeding Bird Survey routes across 18 states, most concentrated in the Appalachian Mountains.
Family
Parulidae · Forest birds

Notable Black-throated Blue 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 →

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 →

Black-throated Blue Warbler has surged in surveyed states: up 105% on the route-weighted index since 1968.

Black-throated Blue Warbler Population Forecast

If the recent trend holds, Black-throated Blue Warbler is projected to rise about 59% by 2030 — from 0.18 in 2025 to a central estimate of 0.29 (95% range 0.22–0.36). A 5-year backtest shows a typical error of ±32.9%, with 40% of held-out values landing inside the 95% band.

+59%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 →
0.29Projected 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 →
0.22–0.3695% 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 →
±32.9%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, Black-throated Blue Warbler is projected to rise about 59% by 2030 — from 0.18 in 2025 to a central estimate of 0.29 (95% range 0.22–0.36). A 5-year backtest shows a typical error of ±32.9%, with 40% 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 →
20260.280.210.35
20270.280.210.35
20280.280.210.35
20290.280.210.35
20300.290.220.36

Where the Black-throated Blue Warbler Is Detected

BBS routes recording Black-throated Blue Warbler, sized by most recent count.

Black-throated Blue Warbler Population Trend by State

Black-throated Blue 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 →
Connecticut-1%196915
Georgiainsufficient datan/a2
Maine+90%196975
Maryland+788%19689
Massachusetts+10%196918
Michigan+601%197349
Minnesota+345%197217
New Hampshire+134%196826
New Jerseyinsufficient datan/a2
New York-17%196882
North Carolina12×197022
Pennsylvania17×196875
Rhode Islandinsufficient datan/a1
Tennessee+679%19685
Vermont+255%196825
Virginia+56%196820
West Virginia17×197025
Wisconsin+392%197521

Black-throated Blue Warbler Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Black-throated Blue 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 →
Boreal Hardwood Transition+866%197181
Lower Great Lakes / St. Lawrence Plain-57%196931
Atlantic Northern Forest+92%1968155
Appalachian Mountains+761%1968183
New England / Mid-Atlantic Coast-5%196829

Black-throated Blue Warbler Conservation Status

Our route-weighted index shows it up about 105% 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.