BirdAnalyst
Species · BCR 13 · BBS 2025 Release · 1966–2024

Common Merganser In Lower Great Lakes / St. Lawrence Plain

All regionsLower Great Lakes / St. Lawrence PlainWaterfowl

Common Merganser in Lower Great Lakes / St. Lawrence Plain has held roughly steady: down 6% on the route-weighted index since 1989.

-6%Since 1989TrendPercent 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 →
27Routes In RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
33YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable 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 Lower Great Lakes / St. Lawrence Plain. See the full index history below.

Common Merganser In Lower Great Lakes / St. Lawrence Plain Population Forecast

If the recent trend holds, Common Merganser in Lower Great Lakes / St. Lawrence Plain is projected to stay roughly flat through 2029, near 0.12 (95% range 0.00–0.32). A 5-year backtest shows a typical error of ±58.3%, with 100% of held-out values landing inside the 95% band.

n/aChange 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 →
0.12Projected 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 →
0.00–0.3295% 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 →
±58.3%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, Common Merganser in Lower Great Lakes / St. Lawrence Plain is projected to stay roughly flat through 2029, near 0.12 (95% range 0.00–0.32). A 5-year backtest shows a typical error of ±58.3%, with 100% of held-out values landing inside the 95% band.19772029
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 →
20250.120.000.31
20260.120.000.31
20270.120.000.31
20280.120.000.31
20290.120.000.32

Routes In Lower Great Lakes / St. Lawrence Plain

Routes recording Common Merganser in Lower Great Lakes / St. Lawrence Plain.
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 →
Harris HillNEW-YORK82019
AusterlitzNEW-YORK52007
Ferris CrnrsPENNSYLVANIA52021
ColchesterVERMONT52018
HighlandNEW-YORK31997
MacdougallNEW-YORK32022
RandolphNEW-YORK22008
Alder CreekNEW-YORK22004
OneidaNEW-YORK22009
North PownalVERMONT22024
ShaftsburyVERMONT22023
CatskillsNEW-YORK12003
GhentNEW-YORK12007
DuanesburgNEW-YORK12018
TrumansburgNEW-YORK12023
Canadice LNEW-YORK12023
Mt MorrisNEW-YORK12007
HamburgNEW-YORK12023
Cherry HillNEW-YORK12015
NashvilleNEW-YORK11995
WatertownNEW-YORK12011
PulaskiNEW-YORK11992
N WilmurtNEW-YORK11992
SalemNEW-YORK12014
Sugar GrovePENNSYLVANIA12001

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