BirdAnalyst
Species · Pennsylvania · BBS 2025 Release · 1966–2024

Chimney Swift Population Trend in Pennsylvania

All statesAerial insectivores

Chimney Swift in Pennsylvania has declined: down 36% on the route-weighted index since 1968.

-36%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 →
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 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 rise about 15% by 2029 — from 6.6 in 2024 to a central estimate of 7.6 (95% range 4.9–10). A 5-year backtest shows a typical error of ±11.2%, with 100% of held-out values landing inside the 95% band.

+15%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 →
7.6Projected 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 →
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 →
±11.2%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 rise about 15% by 2029 — from 6.6 in 2024 to a central estimate of 7.6 (95% range 4.9–10). A 5-year backtest shows a typical error of ±11.2%, with 100% 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 →
20257.75.010
20267.75.010
20277.75.010
20287.64.910
20297.64.910

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 →
Harmonsburg5820231966
West Grove5419961966
Ryde4720051968
Parkwood4220241967
Ephrata4219881969
Aspers4219891968
Portersville4019881973
Slippery Rk3719941970
Wakena3220231969
Patton3120241971
Kittanning2820241973
Mount Joy2820241978
Plesant Grov2720241966
Doylesburg2520232009
Martinsburg2420241970
Sporting Hil2419771977
Scheafferstn2320011966
Beaver2220241969
Pine Gr Mill2220241967
Munson2020241980
Bald Eagle1820241969
Gatchelville1819901972
Brunnerville1720091969
Middletown1620241973
Pottstown1619871966

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 2026-05-22.