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Species · Pennsylvania · BBS 2025 Release · 1966–2024

Carolina Wren Population Trend in Pennsylvania

All statesForest birds

Carolina Wren in Pennsylvania has surged: up 32× on the route-weighted index since 1968.

32×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 →
131Routes 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 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 32× 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 fall about 34% by 2029 — from 9.1 in 2024 to a central estimate of 6.0 (95% range 3.9–8.1). A 5-year backtest shows a typical error of ±28.3%, with 60% of held-out values landing inside the 95% band.

-34%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 →
6.0Projected 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 →
3.9–8.195% 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 →
±28.3%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 fall about 34% by 2029 — from 9.1 in 2024 to a central estimate of 6.0 (95% range 3.9–8.1). A 5-year backtest shows a typical error of ±28.3%, with 60% 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 →
20255.63.57.7
20265.73.67.8
20275.83.77.9
20285.93.88.0
20296.03.98.1

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 →
Stoneybreak3520241992
Peru Mills2720241966
Doylesburg2720232009
Clear Spring2520241970
Mifflintown2520241966
Millville2420241973
Waterstreet2420241969
Collegeville2320241973
Jacobus2220241986
Pine Gr Mill2120241968
Middletown2120241973
Chatham2120241997
Doe Run2020241969
Beaver1920241971
Needmore1919911967
Plesant Grov1720241969
Parkwood1720241967
Ryde1720051969
Landisburg1720241978
Schwenksvill1720241988
Drehersville 21720242000
Berwick1720241986
Geeseytown1620241987
Mount Joy1620241978
Shelocta1520241971

Carolina Wren Population Trend in Other States

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

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