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Species · Pennsylvania · BBS 2025 Release · 1966–2024

Northern Rough-winged Swallow Population Trend in Pennsylvania

All statesAerial insectivores

Northern Rough-winged Swallow in Pennsylvania has surged: up 84% on the route-weighted index since 1968.

+84%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 →
122Routes 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 Northern Rough-winged Swallow 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 →

Northern Rough-winged Swallow has surged in Pennsylvania: up 84% on the route-weighted index since 1968.

Northern Rough-winged Swallow Population Forecast in Pennsylvania

If the recent trend holds, Northern Rough-winged Swallow in Pennsylvania is projected to fall about 23% by 2029 — from 1.5 in 2024 to a central estimate of 1.1 (95% range 0.68–1.6). A 5-year backtest shows a typical error of ±15.3%, with 100% of held-out values landing inside the 95% band.

-23%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 →
1.1Projected 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 →
0.68–1.695% 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 →
±15.3%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, Northern Rough-winged Swallow in Pennsylvania is projected to fall about 23% by 2029 — from 1.5 in 2024 to a central estimate of 1.1 (95% range 0.68–1.6). A 5-year backtest shows a typical error of ±15.3%, 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 →
20251.10.651.6
20261.10.651.6
20271.10.661.6
20281.10.671.6
20291.10.681.6

Northern Rough-winged Swallow Survey Routes in Pennsylvania

Routes recording Northern Rough-winged Swallow 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 →
Mount Joy2420241979
Brick Tavern1520241994
Beaver1220241969
Stoneybreak920221992
Betula820221989
Portersville819881988
Elizabethvil820241997
New Ringgold720241966
Schaefferstown 2720242002
Russell City620071969
Rush620241970
Doubling Gap619761966
Ramsey520231992
Pocono Summit520241994
Susquehanna520241978
Kaylor520221968
Rector519661966
Drehersville519991967
Doylesburg520232013
Eldred420082005
Marsh Hill420071985
Duvall420171977
Shelocta420241972
Carsonville420231966
West Grove419961970

Northern Rough-winged Swallow Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonrhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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