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

Common Merganser Population Trend in Washington

All statesWaterfowl

Common Merganser in Washington has held roughly steady: down 3% on the route-weighted index since 1971.

-3%Since 1971TrendPercent 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 →
53Routes 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 →
55YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Common 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 →

No notable trend signals for Common Merganser in Washington. See the full index history below.

Common Merganser Population Forecast in Washington

If the recent trend holds, Common Merganser in Washington is projected to rise about 23% by 2029 — from 0.39 in 2024 to a central estimate of 0.48 (95% range 0.03–0.92). A 5-year backtest shows a typical error of ±19.6%, with 100% of held-out values landing inside the 95% band.

+23%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 →
0.48Projected 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 →
0.03–0.9295% 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 →
±19.6%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 Washington is projected to rise about 23% by 2029 — from 0.39 in 2024 to a central estimate of 0.48 (95% range 0.03–0.92). A 5-year backtest shows a typical error of ±19.6%, with 100% of held-out values landing inside the 95% band.19692029
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 →
20250.460.010.91
20260.460.010.91
20270.470.020.92
20280.470.020.92
20290.480.030.92

Common Merganser Survey Routes in Washington

Routes recording Common 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 →
Deception8420172017
Warm Beach820051970
Rimrock820231980
No Cascades619961996
Nighthawk620241996
Newhalem520241969
Taholah520221978
Sullivan Lk519991999
Brewster420152015
Leavenworth419901984
South Elma420171986
Sullivan Lake 2320232000
Spring Lake320212018
Hurricane Rg320231992
Yakima320241993
Twisp220241969
Bunker Hill219981985
Ronald220241973
Ilwaco219961995
White Chuck220231992
Horn Rapids220192008
Mt St Helens220021994
Laurier220181999
Rainier220041996
Ozette120241974

Common Merganser Population Trend in Other States

alaskaarizonacaliforniacoloradoconnecticutidahomainemarylandmassachusettsmichiganminnesotamontananevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-dakotaohiooregonpennsylvaniasouth-dakotautahvermontvirginiawest-virginiawisconsinwyoming

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