BirdAnalyst
Species · Pennsylvania · BBS 2026 Release · 1966–2025

Chimney Swift Population Trend in Pennsylvania

All statesAerial insectivores

Chimney Swift in Pennsylvania has declined: down 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 Chimney Swift 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 →

No notable trend signals for Chimney Swift in Pennsylvania. See the full index history below.

Chimney Swift Population Forecast in Pennsylvania

If the recent trend holds, Chimney Swift in Pennsylvania is projected to stay roughly flat through 2030, near 7.6 (95% range 4.9–10). A 5-year backtest shows a typical error of ±9.2%, with 100% of held-out values landing inside the 95% band.

+2%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 →
7.6Projected 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 →
4.9–1095% 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 →
±9.2%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, Chimney Swift in Pennsylvania is projected to stay roughly flat through 2030, near 7.6 (95% range 4.9–10). A 5-year backtest shows a typical error of ±9.2%, with 100% 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 →
20267.75.010
20277.75.010
20287.75.010
20297.64.910
20307.64.910

Chimney Swift Survey Routes in Pennsylvania

Routes recording Chimney Swift 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 →
West Grove5419961966
Ryde4720051968
Ephrata4219881969
Aspers4219891968
Portersville4019881973
Kittanning4020251973
Slippery Rk3719941970
Beaver3620251969
Parkwood3620251967
Harmonsburg3220251966
N Washington3220251967
Wakena3220231969
Bald Eagle3220251969
Patton3120241971
Plesant Grov2720241966
Doylesburg2520232009
Leola2520251998
Sporting Hil2419771977
Scheafferstn2320011966
Martinsburg2120251970
Clover1920251981
Munson1820251980
Gatchelville1819901972
Brunnerville1720091969
Rosecrans1620251969

Chimney Swift Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooklahomarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsinwyoming

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