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Species · Pennsylvania · BBS 2026 Release · 1966–2025

Willow Flycatcher Population Trend in Pennsylvania

All statesAerial insectivores

Willow Flycatcher in Pennsylvania has surged: up 106% on the route-weighted index since 1968.

+106%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 →
118Routes 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 Willow Flycatcher 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 →

Willow Flycatcher has surged in Pennsylvania: up 106% on the route-weighted index since 1968.

Willow Flycatcher Population Forecast in Pennsylvania

If the recent trend holds, Willow Flycatcher in Pennsylvania is projected to rise about 71% by 2030 — from 1.1 in 2025 to a central estimate of 2.0 (95% range 0.97–3.0). A 5-year backtest shows a typical error of ±68.3%, with 60% of held-out values landing inside the 95% band.

+71%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 →
2.0Projected 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 →
0.97–3.095% 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 →
±68.3%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, Willow Flycatcher in Pennsylvania is projected to rise about 71% by 2030 — from 1.1 in 2025 to a central estimate of 2.0 (95% range 0.97–3.0). A 5-year backtest shows a typical error of ±68.3%, with 60% 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 →
20261.90.932.9
20271.90.942.9
20281.90.952.9
20291.90.962.9
20302.00.973.0

Willow Flycatcher Survey Routes in Pennsylvania

Routes recording Willow Flycatcher 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 Grove1419961967
Drehersville 21120252000
Jefferson820251966
Harmonsburg720251966
Doe Run720251969
Plesant Grov620241970
Drehersville619991966
Waller520251974
Quakertown519891972
Espyville420251976
Teepleville420241966
Roulette420161989
Beaver420251978
Kaylor420251995
Clover320251988
Arnot320251998
Portersville319881974
Kittanning320231973
Brunnerville320091970
Mt Gretna 2320192015
Brunnerville 2320252010
Betula220221987
Ramsey220221975
Little Marsh220241993
Rush220251986

Willow Flycatcher Population Trend in Other States

alaskaarizonaarkansascaliforniacoloradoconnecticutdelawaregeorgiaidahoillinoisindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonrhode-islandsouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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