BirdAnalyst
Species · Pennsylvania · BBS 2025 Release · 1966–2024

Worm-eating Warbler Population Trend in Pennsylvania

All statesForest birds

Worm-eating Warbler in Pennsylvania has surged: up 142% on the route-weighted index since 1968.

+142%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 →
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 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 142% 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 stay roughly flat through 2029, near 0.51 (95% range 0.31–0.70). A 5-year backtest shows a typical error of ±22%, with 100% of held-out values landing inside the 95% band.

-6%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 →
0.51Projected 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 →
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 →
±22%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 stay roughly flat through 2029, near 0.51 (95% range 0.31–0.70). A 5-year backtest shows a typical error of ±22%, 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 →
20250.490.290.68
20260.490.290.69
20270.500.300.69
20280.500.300.70
20290.510.310.70

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 →
St College820241970
Stoneybreak620241992
Tussey Mtn.620241993
Geeseytown420241987
Roulette 2420232023
Duboistown420241990
Landisburg420241978
Starlight319901975
Ryde320051970
South Mtn320231986
Logue220232023
Cherry Sprs220001977
Virginia219771971
Williamsburg220241988
Waterstreet220241970
Doubling Gap219671966
New Ringgold220241966
Schwenksvill220022002
Berwick220241988
Broad Mtn.220241994
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 2026-05-22.