BirdAnalyst
Species · Montana · BBS 2026 Release · 1966–2025

Common Merganser Population Trend in Montana

All statesWaterfowl

Common Merganser in Montana has surged: up 367% on the route-weighted index since 1975.

+367%Since 1975TrendPercent 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 →
45Routes 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 →
50YearsYears 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 MontanaNotable 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 Montana. See the full index history below.

Common Merganser Population Forecast in Montana

If the recent trend holds, Common Merganser in Montana is projected to rise about 13% by 2030 — from 0.22 in 2025 to a central estimate of 0.24 (95% range 0.01–0.47). A 5-year backtest shows a typical error of ±46.4%, with 100% of held-out values landing inside the 95% band.

+13%Change by 2030TrendPercent 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 →
0.24Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.01–0.4795% 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 →
±46.4%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 Montana is projected to rise about 13% by 2030 — from 0.22 in 2025 to a central estimate of 0.24 (95% range 0.01–0.47). A 5-year backtest shows a typical error of ±46.4%, with 100% of held-out values landing inside the 95% band.19722030
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 →
20260.240.010.47
20270.240.010.47
20280.240.010.47
20290.240.010.47
20300.240.010.47

Common Merganser Survey Routes in Montana

Routes recording Common Merganser in Montana.
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 →
Beaverhead819971981
Kalispell620071981
Fish Creek620192003
Libby Dam520241979
Great Falls419951973
Flatwillow419771977
Red Rock419891975
East Glacier Park420252016
Augusta319971986
Swan Lake320232021
Maynard Coulee320222022
Hebgen Lake320252017
Willow Creek 2220071983
St Xavier 2220182018
Circle220001997
Two Dot220241976
Thompson Riv220211996
Wheat Basin220192019
Lima220251999
St Mary120001991
Logan Pass120121988
Glen120251992
St Regis120141978
Arlee120251981
Highwood120241990

Common Merganser Population Trend in Other States

alaskaarizonacaliforniacoloradoconnecticutidahomainemarylandmassachusettsmichiganminnesotanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-dakotaohiooregonpennsylvaniasouth-dakotautahvermontvirginiawashingtonwest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.