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

Hooded Merganser In Lower Great Lakes / St. Lawrence Plain

All regionsLower Great Lakes / St. Lawrence PlainWaterfowl

Hooded Merganser in Lower Great Lakes / St. Lawrence Plain has fallen sharply: down 52% on the route-weighted index since 1985.

-52%Since 1985TrendPercent 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 →
20Routes 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 →
29YearsYears 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 →

long arc declinecomputed 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 →

Hooded Merganser has fallen sharply in Lower Great Lakes / St. Lawrence Plain: down 52% on the route-weighted index since 1985.

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

If the recent trend holds, Hooded Merganser in Lower Great Lakes / St. Lawrence Plain is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.09). A 5-year backtest shows a typical error of ±48.3%, 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 →
0.01Projected 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 →
0.00–0.0995% 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 →
±48.3%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, Hooded Merganser in Lower Great Lakes / St. Lawrence Plain is projected to stay roughly flat through 2029, near 0.01 (95% range 0.00–0.09). A 5-year backtest shows a typical error of ±48.3%, 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 →
20250.020.000.09
20260.020.000.09
20270.010.000.09
20280.010.000.09
20290.010.000.09

Routes In Lower Great Lakes / St. Lawrence Plain

Routes recording Hooded 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 →
TrumansburgNEW-YORK82000
DuanesburgNEW-YORK31997
Oriskany FlsNEW-YORK22022
HamburgNEW-YORK22013
Cherry HillNEW-YORK21982
Ferris CrnrsPENNSYLVANIA22004
HighlandNEW-YORK12012
CastileNEW-YORK12010
E YoungstownNEW-YORK12013
N WilmurtNEW-YORK11985
North EastonNEW-YORK12006
OgdensburgNEW-YORK12018
PhiladelphiaNEW-YORK12019
PittsfieldOHIO12011
HiramOHIO12007
EspyvillePENNSYLVANIA12013
HarmonsburgPENNSYLVANIA12017
TeeplevillePENNSYLVANIA12009
ShaftsburyVERMONT12024
Grand IsleVERMONT12024

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