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Species · Pennsylvania · BBS 2026 Release · 1966–2025

Carolina Wren Population Trend in Pennsylvania

All statesForest birds

Carolina Wren in Pennsylvania has surged: up 33× on the route-weighted index since 1968.

33×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 →
133Routes 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 Carolina Wren 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 →

Carolina Wren has surged in Pennsylvania: up 33× on the route-weighted index since 1968.

Carolina Wren Population Forecast in Pennsylvania

If the recent trend holds, Carolina Wren in Pennsylvania is projected to stay roughly flat through 2030, near 6.2 (95% range 4.1–8.3). A 5-year backtest shows a typical error of ±24.7%, with 80% of held-out values landing inside the 95% band.

-7%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 →
6.2Projected 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 →
4.1–8.395% 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 →
±24.7%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, Carolina Wren in Pennsylvania is projected to stay roughly flat through 2030, near 6.2 (95% range 4.1–8.3). A 5-year backtest shows a typical error of ±24.7%, 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 →
20265.83.77.9
20275.93.88.0
20286.03.98.1
20296.14.08.2
20306.24.18.3

Carolina Wren Survey Routes in Pennsylvania

Routes recording Carolina Wren 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 →
Doylesburg2720232009
Chatham2720251997
Waterstreet2420241969
Beaver2320251971
Collegeville2320241973
Mifflintown2220251966
Millville2020251973
Needmore1919911967
Drehersville 21820252000
Plesant Grov1720241969
Ryde1720051969
Schwenksvill1720241988
Berwick1720251986
Ramsey1620251970
Pine Gr Mill1620251968
Doe Run1620251969
Geeseytown1520251987
Elizabethvil1520251995
Stoneybreak1520251992
Jacobus1520251986
N Washington1420251975
Kittanning1320251973
Naginey1320251973
Landisburg1320251978
Mt Gretna 21320222001

Carolina Wren Population Trend in Other States

alabamaarkansasconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanew-hampshirenew-jerseynew-yorknorth-carolinaohiooklahomarhode-islandsouth-carolinatennesseetexasvermontvirginiawest-virginiawisconsin

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