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

Common Merganser Population Trend in Wisconsin

All statesWaterfowl

Common Merganser in Wisconsin has surged: up 137% on the route-weighted index since 1972.

+137%Since 1972TrendPercent 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 →
39YearsYears 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 WisconsinNotable 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 Wisconsin. See the full index history below.

Common Merganser Population Forecast in Wisconsin

If the recent trend holds, Common Merganser in Wisconsin is projected to fall about 42% by 2029 — from 0.07 in 2024 to a central estimate of 0.04 (95% range 0.00–0.09). A 5-year backtest shows a typical error of ±135.4%, with 100% of held-out values landing inside the 95% band.

-42%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 →
0.04Projected 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 →
0.00–0.0995% 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 →
±135.4%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 Wisconsin is projected to fall about 42% by 2029 — from 0.07 in 2024 to a central estimate of 0.04 (95% range 0.00–0.09). A 5-year backtest shows a typical error of ±135.4%, with 100% of held-out values landing inside the 95% band.19672029
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 →
20250.040.000.08
20260.040.000.09
20270.040.000.09
20280.040.000.09
20290.040.000.09

Common Merganser Survey Routes in Wisconsin

Routes recording Common Merganser in Wisconsin.
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 →
Gresham520242024
Mcnaughton320131991
Dresser219841971
Gilman220042004
Crandon220182006
Iron River120072007
Bayfield120231992
Shanagolden119781978
Montreal120061984
Land O Lakes120131967
Hudson120091999
Union Twp119891989
Couderay120182004
Exeland119941983
Rib Lake120151990
Eagle River120102010
Popple River119871973
Amberg120081989
Washington I120241986
Cochrane119791979
Trempealeau119721972
Wis Rapids120192019
Manawa120082001
Conover120222004
Weirgor Springs120142014

Common Merganser Population Trend in Other States

alaskaarizonacaliforniacoloradoconnecticutidahomainemarylandmassachusettsmichiganminnesotamontananevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-dakotaohiooregonpennsylvaniasouth-dakotautahvermontvirginiawashingtonwest-virginiawyoming

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