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Species · Pennsylvania · BBS 2025 Release · 1966–2024

Black-throated Green Warbler Population Trend in Pennsylvania

All statesForest birds

Black-throated Green Warbler in Pennsylvania has surged: up 24× on the route-weighted index since 1968.

24×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 →
58YearsYears 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 24× 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 24% by 2029 — from 4.0 in 2024 to a central estimate of 5.0 (95% range 3.3–6.7). A 5-year backtest shows a typical error of ±34.8%, with 100% of held-out values landing inside the 95% band.

+24%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 →
5.0Projected 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 →
3.3–6.795% 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 →
±34.8%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 24% by 2029 — from 4.0 in 2024 to a central estimate of 5.0 (95% range 3.3–6.7). A 5-year backtest shows a typical error of ±34.8%, with 100% of held-out values landing inside the 95% band.19662029
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 →
20254.73.06.4
20264.73.06.4
20274.83.16.5
20284.93.26.6
20295.03.36.7

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 →
Lynch2420241968
Duboistown1920241987
Tussey Mtn.1920241993
Odin1820241973
St College1820241970
Roulette1720211977
Munson1720241981
Ridgway1620181988
Ellenton1620241982
Russell City1520241968
Roulette 21520242022
Cherry Sprs1420231974
Marsh Hill1420241983
Broad Mtn.1420241993
N Pine Grove1320241969
Laurel Hill1320241978
Ansonia1320242002
Sproul Sf-B1320242002
Rasselas1120221969
Sproul Sf-A1120242002
Pottersdale1020241968
English Ctr1019891970
Ltl Pine Cr1020241990
Mill Run1020241978
Rothrock Sf920191992

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 2026-05-22.