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Species · Pennsylvania · BBS 2025 Release · 1966–2024

Chestnut-sided Warbler Population Trend in Pennsylvania

All statesForest birds

Chestnut-sided Warbler in Pennsylvania has surged: up 107% on the route-weighted index since 1968.

+107%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 →
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 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 107% 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 13% by 2029 — from 4.3 in 2024 to a central estimate of 4.9 (95% range 3.7–6.1). A 5-year backtest shows a typical error of ±16.6%, with 80% of held-out values landing inside the 95% band.

+13%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 →
4.9Projected 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 →
3.7–6.195% 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 →
±16.6%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 13% by 2029 — from 4.3 in 2024 to a central estimate of 4.9 (95% range 3.7–6.1). A 5-year backtest shows a typical error of ±16.6%, with 80% 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 →
20254.73.55.8
20264.73.65.9
20274.83.65.9
20284.83.76.0
20294.93.76.1

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 →
Odin4820241975
Roulette2820211970
Eldred2520221974
Poyntelle2520241969
Duboistown2220241987
Susquehanna2120241971
Sugar Grove1920241981
Starlight1819991970
Sproul Sf-A1820242002
Roulette 21720242022
Laurel Hill1620241978
Sproul Sf-B1420242002
Ridgway1320181967
Honesdale1220241972
Marsh Hill1120241985
Mill Run1120241978
Betula1020221973
Cherry Sprs1020231974
Logue920231970
Starlight 2920242000
Ansonia920242002
Arnot820241969
Greentown820241973
Munson820241980
Ellenton820241982

Chestnut-sided Warbler Population Trend in Other States

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

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.