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

Hooded Merganser Population Trend in Washington

All statesWaterfowl

Hooded Merganser in Washington has fallen sharply: down 64% on the route-weighted index since 1988.

-64%Since 1988TrendPercent 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 →
26Routes 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 WashingtonNotable 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 Washington: down 64% on the route-weighted index since 1988.

Hooded Merganser Population Forecast in Washington

If the recent trend holds, Hooded Merganser in Washington is projected to fall about 64% by 2029 — from 0.05 in 2024 to a central estimate of 0.02 (95% range 0.00–0.08). A 5-year backtest shows a typical error of ±74.8%, with 80% of held-out values landing inside the 95% band.

-64%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 →
0.02Projected 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 →
0.00–0.0895% 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 →
±74.8%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 Washington is projected to fall about 64% by 2029 — from 0.05 in 2024 to a central estimate of 0.02 (95% range 0.00–0.08). A 5-year backtest shows a typical error of ±74.8%, with 80% of held-out values landing inside the 95% band.19752029
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 →
20250.030.000.09
20260.020.000.09
20270.020.000.08
20280.020.000.08
20290.020.000.08

Hooded Merganser Survey Routes in Washington

Routes recording Hooded Merganser in Washington.
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 →
Mendota519881988
Twin Lakes419991999
Pe Ell319971997
Montesand219931990
Ilwaco220222022
Nighthawk220132008
Ozette120091999
Port Angeles120231998
Warm Beach120101975
Newhalem119891989
Twisp120242013
Deception119951992
Turnbull Nwr120172016
L Pend O Nwr119971997
Mendota 2119951989
Columbia Nwr120212021
Camas119951995
Kendall120211996
South Elma120241984
Packwood120132009
Carlton119981998
Hurricane Rg120232023
Omak Creek120242009
Laurier120212011
Rainier120192019

Hooded Merganser Population Trend in Other States

alabamaalaskaarkansascoloradoconnecticutidahoillinoisindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanew-hampshirenew-yorknorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontwest-virginiawisconsinwyoming

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