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Species · Pennsylvania · BBS 2026 Release · 1966–2025

Black-throated Green Warbler Population Trend in Pennsylvania

All statesForest birds

Black-throated Green Warbler in Pennsylvania has surged: up 23× on the route-weighted index since 1968.

23×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 →
100Routes 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 →
59YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Black-throated Green Warbler Trends in PennsylvaniaNotable 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 Green Warbler has surged in Pennsylvania: up 23× on the route-weighted index since 1968.

Black-throated Green Warbler Population Forecast in Pennsylvania

If the recent trend holds, Black-throated Green Warbler in Pennsylvania is projected to rise about 48% by 2030 — from 3.3 in 2025 to a central estimate of 4.9 (95% range 3.2–6.6). A 5-year backtest shows a typical error of ±31.2%, with 100% of held-out values landing inside the 95% band.

+48%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 →
4.9Projected 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 →
3.2–6.695% 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 →
±31.2%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 Green Warbler in Pennsylvania is projected to rise about 48% by 2030 — from 3.3 in 2025 to a central estimate of 4.9 (95% range 3.2–6.6). A 5-year backtest shows a typical error of ±31.2%, with 100% 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 →
20264.62.96.4
20274.73.06.4
20284.83.16.5
20294.93.16.6
20304.93.26.6

Black-throated Green Warbler Survey Routes in Pennsylvania

Routes recording Black-throated Green Warbler in Pennsylvania.
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 →
Russell City2120251968
Ansonia2020252002
Odin1920251973
Duboistown1920241987
Roulette1720211977
Lynch1620251968
Ridgway1620181988
Munson1520251981
Ellenton1420251982
Pottersdale1320251968
Tussey Mtn.1320251993
Rasselas1120221969
Cherry Sprs1120251974
Roulette 21120252022
Mill Run1120251978
Broad Mtn.1120251993
English Ctr1019891970
Mawr Glen1020251982
St College1020251970
Sproul Sf-A1020252002
Rothrock Sf920191992
N Pine Grove720251969
Logue720251976
Ltl Pine Cr620251990
Marsh Hill520251983

Black-throated Green Warbler Population Trend in Other States

alabamaarkansasconnecticutgeorgiaindianakentuckymainemarylandmassachusettsmichiganminnesotamissourinew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomarhode-islandsouth-carolinatennesseevermontvirginiawest-virginiawisconsin

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