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Species · Pennsylvania · BBS 2026 Release · 1966–2025

Worm-eating Warbler Population Trend in Pennsylvania

All statesForest birds

Worm-eating Warbler in Pennsylvania has surged: up 155% on the route-weighted index since 1968.

+155%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 →
86Routes 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 Worm-eating 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 →

Worm-eating Warbler has surged in Pennsylvania: up 155% on the route-weighted index since 1968.

Worm-eating Warbler Population Forecast in Pennsylvania

If the recent trend holds, Worm-eating Warbler in Pennsylvania is projected to rise about 16% by 2030 — from 0.44 in 2025 to a central estimate of 0.51 (95% range 0.31–0.70). A 5-year backtest shows a typical error of ±14.5%, with 100% of held-out values landing inside the 95% band.

+16%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 →
0.51Projected 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 →
0.31–0.7095% 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 →
±14.5%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, Worm-eating Warbler in Pennsylvania is projected to rise about 16% by 2030 — from 0.44 in 2025 to a central estimate of 0.51 (95% range 0.31–0.70). A 5-year backtest shows a typical error of ±14.5%, 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 →
20260.490.290.68
20270.490.300.69
20280.500.300.69
20290.500.310.70
20300.510.310.70

Worm-eating Warbler Survey Routes in Pennsylvania

Routes recording Worm-eating 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 →
Naginey820251976
Tussey Mtn.820251993
Broad Mtn.520251994
Roulette 2420232023
Duboistown420241990
Landisburg420241978
Starlight319901975
Ryde320051970
Logue220232023
Cherry Sprs220001977
Virginia219771971
Williamsburg220251988
Geeseytown220251987
Waterstreet220241970
Doubling Gap219671966
St College220251970
Pine Gr Mill220251969
Schwenksvill220022002
South Mtn220251986
Berwick220241988
Ansonia220092009
Sproul Sf-B220222002
Lynch120072007
N Washington120022002
N Pine Grove119991989

Worm-eating Warbler Population Trend in Other States

alabamaarkansasconnecticutdelawaregeorgiaillinoisindianaiowakentuckylouisianamarylandmassachusettsmississippimissourinew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomarhode-islandsouth-carolinatennesseetexasvirginiawest-virginiawisconsin

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