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

Hooded Merganser Population Trend in Maine

All statesWaterfowl

Hooded Merganser in Maine has surged: up 233% on the route-weighted index since 1991.

+233%Since 1991TrendPercent 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 StateSurvey 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 Hooded Merganser Trends in MaineNotable 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 →

Hooded Merganser has surged in Maine: up 233% on the route-weighted index since 1991.

Hooded Merganser Population Forecast in Maine

If the recent trend holds, Hooded Merganser in Maine is projected to stay roughly flat through 2029, near 0.15 (95% range 0.01–0.30). A 5-year backtest shows a typical error of ±41.2%, with 80% of held-out values landing inside the 95% band.

-3%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 →
0.15Projected 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 →
0.01–0.3095% 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 →
±41.2%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 Maine is projected to stay roughly flat through 2029, near 0.15 (95% range 0.01–0.30). A 5-year backtest shows a typical error of ±41.2%, with 80% of held-out values landing inside the 95% band.19792029
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 →
20250.140.000.29
20260.140.000.29
20270.150.000.29
20280.150.000.30
20290.150.010.30

Hooded Merganser Survey Routes in Maine

Routes recording Hooded Merganser in Maine.
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 →
Stacyville720212021
Bowdoin Ctr619941994
Harmony320241997
Brownfield 2320212021
Brooks220132013
Carrabassett220082008
Charleston219931993
Jefferson220081991
Newcastle120032003
Wilson Mills120191997
Greenwood120172017
Reeds120102010
Otisfield Gr120142013
Hartford120092009
Manchester119821982
Eastbrook120192019
Hancock120101979
Aurora120172017
Carrying Pl120232003
Seboomook Lk120132002
Lake Moxie120062006
Washburn120051996
Cornville120222019
Boundary120152015
St David120052004

Hooded Merganser Population Trend in Other States

alabamaalaskaarkansascoloradoconnecticutidahoillinoisindianaiowakansaskentuckymarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-yorknorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontwashingtonwest-virginiawisconsinwyoming

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