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Species · Pennsylvania · BBS 2026 Release · 1966–2025

Chestnut-sided Warbler Population Trend in Pennsylvania

All statesForest birds

Chestnut-sided Warbler in Pennsylvania has surged: up 99% on the route-weighted index since 1968.

+99%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 →
112Routes 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 Chestnut-sided 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 →

Chestnut-sided Warbler has surged in Pennsylvania: up 99% on the route-weighted index since 1968.

Chestnut-sided Warbler Population Forecast in Pennsylvania

If the recent trend holds, Chestnut-sided Warbler in Pennsylvania is projected to rise about 14% by 2030 — from 4.3 in 2025 to a central estimate of 4.9 (95% range 3.8–6.1). A 5-year backtest shows a typical error of ±14.4%, with 80% of held-out values landing inside the 95% band.

+14%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 →
3.8–6.195% 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 →
±14.4%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, Chestnut-sided Warbler in Pennsylvania is projected to rise about 14% by 2030 — from 4.3 in 2025 to a central estimate of 4.9 (95% range 3.8–6.1). A 5-year backtest shows a typical error of ±14.4%, with 80% 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 →
20264.73.55.9
20274.73.65.9
20284.83.66.0
20294.93.76.0
20304.93.86.1

Chestnut-sided Warbler Survey Routes in Pennsylvania

Routes recording Chestnut-sided 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 →
Odin3820251975
Poyntelle3420251969
Roulette2820211970
Eldred2520221974
Logue2220251970
Duboistown2220241987
Ansonia1920252002
Starlight1819991970
Honesdale1520251972
Sugar Grove1520251981
Mill Run1520251978
Ridgway1320181967
Susquehanna1320251971
Roulette 21320252022
Sproul Sf-A1320252002
Cherry Sprs1220251974
Pottersdale1020251968
Betula1020221973
Arnot920251969
Sproul Sf-B920252002
N Pine Grove820251969
Russell City820251968
Marsh Hill820251985
Greentown820241973
Munson820251980

Chestnut-sided Warbler Population Trend in Other States

alabamaarkansascoloradoconnecticutgeorgiaillinoisindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotanevadanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiorhode-islandtennesseevermontvirginiawest-virginiawisconsinwyoming

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