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

Common Merganser Population Trend in Pennsylvania

All statesWaterfowl

Common Merganser in Pennsylvania has surged: up 935% on the route-weighted index since 1978.

+935%Since 1978TrendPercent 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 →
54Routes 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 →
47YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Common Merganser 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 →

Common Merganser has surged in Pennsylvania: up 935% on the route-weighted index since 1978.

Common Merganser Population Forecast in Pennsylvania

If the recent trend holds, Common Merganser in Pennsylvania is projected to rise about 42% by 2029 — from 0.24 in 2024 to a central estimate of 0.33 (95% range 0.00–0.83). A 5-year backtest shows a typical error of ±79.4%, with 100% of held-out values landing inside the 95% band.

+42%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 →
0.33Projected 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 →
0.00–0.8395% 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 →
±79.4%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, Common Merganser in Pennsylvania is projected to rise about 42% by 2029 — from 0.24 in 2024 to a central estimate of 0.33 (95% range 0.00–0.83). A 5-year backtest shows a typical error of ±79.4%, with 100% of held-out values landing inside the 95% band.19752029
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 →
20250.310.000.81
20260.320.000.82
20270.320.000.82
20280.330.000.83
20290.330.000.83

Common Merganser Survey Routes in Pennsylvania

Routes recording Common Merganser 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 →
Berwick919931993
Rush920242008
Eldred820152004
Pocono Summit820241997
Ferris Crnrs520211997
Susquehanna420232002
Wyalusing320221988
Lynch320191994
Rasselas320142004
Arnot320041994
Waller320181998
Kittanning320192009
New Ringgold320122012
Betula220191987
Roulette220081999
Ramsey220221995
Mawr Glen220231983
Bow Bridge220211989
Poyntelle220061975
Clearfield220051996
Ellenton120242005
Whig Hill120211985
Sigel120232011
N Washington120172015
Starlight 2120182018

Common Merganser Population Trend in Other States

alaskaarizonacaliforniacoloradoconnecticutidahomainemarylandmassachusettsmichiganminnesotamontananevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-dakotaohiooregonsouth-dakotautahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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