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Species · North Dakota · BBS 2025 Release · 1966–2024

Hooded Merganser Population Trend in North Dakota

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Hooded Merganser in North Dakota has surged: up 11× on the route-weighted index since 1991.

11×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 →
20Routes 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 →
32YearsYears 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 North DakotaNotable 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 North Dakota: up 11× on the route-weighted index since 1991.

Hooded Merganser Population Forecast in North Dakota

If the recent trend holds, Hooded Merganser in North Dakota is projected to fall about 20% by 2029 — from 0.33 in 2024 to a central estimate of 0.27 (95% range 0.03–0.50). A 5-year backtest shows a typical error of ±67.1%, with 60% of held-out values landing inside the 95% band.

-20%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 →
0.27Projected 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 →
0.03–0.5095% 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 →
±67.1%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 North Dakota is projected to fall about 20% by 2029 — from 0.33 in 2024 to a central estimate of 0.27 (95% range 0.03–0.50). A 5-year backtest shows a typical error of ±67.1%, with 60% of held-out values landing inside the 95% band.19682029
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 →
20250.250.010.48
20260.250.020.48
20270.260.020.49
20280.260.030.49
20290.270.030.50

Hooded Merganser Survey Routes in North Dakota

Routes recording Hooded Merganser in North Dakota.
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 →
Forman320222011
Carpio320031996
Denbigh320221991
Lake George220222022
Cooperstown220242014
Horsehead Lk220241994
Buchanan220241968
Lakota220052005
Rolla220222014
Niles220131994
Braddock220142014
Turtle Mtns220221995
Danzig120092003
Emerado120041996
Loraine119891989
Wild Rose120082008
Sheyenne Lk120241998
Montpelier120242012
Danzig 2120242024
Lakota 2120142012

Hooded Merganser Population Trend in Other States

alabamaalaskaarkansascoloradoconnecticutidahoillinoisindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-yorkohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontwashingtonwest-virginiawisconsinwyoming

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