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

Common Merganser Population Trend in Pennsylvania

All statesWaterfowl

Common Merganser in Pennsylvania has surged: up 929% on the route-weighted index since 1978.

+929%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 →
56Routes 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 →
48YearsYears 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 →

No notable trend signals for Common Merganser in Pennsylvania. See the full index history below.

Common Merganser Population Forecast in Pennsylvania

If the recent trend holds, Common Merganser in Pennsylvania is projected to rise about 155% by 2030 — from 0.13 in 2025 to a central estimate of 0.32 (95% range 0.00–0.82). A 5-year backtest shows a typical error of ±100.4%, with 100% of held-out values landing inside the 95% band.

+155%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 →
0.32Projected 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 →
0.00–0.8295% 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 →
±100.4%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 155% by 2030 — from 0.13 in 2025 to a central estimate of 0.32 (95% range 0.00–0.82). A 5-year backtest shows a typical error of ±100.4%, with 100% of held-out values landing inside the 95% band.19752030
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 →
20260.300.000.80
20270.310.000.81
20280.310.000.81
20290.320.000.81
20300.320.000.82

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
Mawr Glen320251983
Waller320181998
Kittanning320192009
New Ringgold320122012
Lovelton220252011
Betula220191987
Roulette220081999
Ramsey220221995
Honesdale220251977
Poyntelle220061975
Clearfield220051996
Ellenton120242005
Whig Hill120211985
Teepleville120252025
Sigel120232011

Common Merganser Population Trend in Other States

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

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