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

Alder Flycatcher Population Trend in Pennsylvania

All statesAerial insectivores

Alder Flycatcher in Pennsylvania has surged: up 314% on the route-weighted index since 1973.

+314%Since 1973TrendPercent 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 →
78Routes 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 →
54YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Alder 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 →

Alder Flycatcher has surged in Pennsylvania: up 314% on the route-weighted index since 1973.

Alder Flycatcher Population Forecast in Pennsylvania

If the recent trend holds, Alder Flycatcher in Pennsylvania is projected to rise about 54% by 2030 — from 0.39 in 2025 to a central estimate of 0.60 (95% range 0.34–0.87). A 5-year backtest shows a typical error of ±71.4%, with 20% of held-out values landing inside the 95% band.

+54%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 →
0.60Projected 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 →
0.34–0.8795% 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 →
±71.4%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, Alder Flycatcher in Pennsylvania is projected to rise about 54% by 2030 — from 0.39 in 2025 to a central estimate of 0.60 (95% range 0.34–0.87). A 5-year backtest shows a typical error of ±71.4%, with 20% of held-out values landing inside the 95% band.19712030
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 →
20260.570.300.83
20270.570.310.84
20280.580.320.85
20290.590.330.86
20300.600.340.87

Alder Flycatcher Survey Routes in Pennsylvania

Routes recording Alder 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 →
Little Marsh820231993
Ellenton720251982
Eldred620151990
Roulette520211988
Austinville520251982
Rasselas420221999
Logue420251981
Starlight419921992
Greentown420241977
Sugar Grove420251995
Poyntelle320251993
Roulette 2320252022
Ferris Crnrs220241973
Whig Hill220031989
Akeley219761974
N Pine Grove219971997
Betula220221987
Mawr Glen220191985
Marsh Hill220251991
New Ringgold219851979
Mars219941994
Espyville120251975
Clover120131989
Harmonsburg120231973
Teepleville120251995

Alder Flycatcher Population Trend in Other States

alaskaconnecticutidahoillinoisindianaiowamainemarylandmassachusettsmichiganminnesotamontananew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooklahomasouth-dakotavermontvirginiawashingtonwest-virginiawisconsin

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