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

Common Merganser Population Trend in Colorado

All statesWaterfowl

Common Merganser in Colorado has surged: up 232% on the route-weighted index since 1980.

+232%Since 1980TrendPercent 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 →
44Routes 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 →
45YearsYears 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 ColoradoNotable 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 →

Common Merganser has surged in Colorado: up 232% on the route-weighted index since 1980.

Common Merganser Population Forecast in Colorado

If the recent trend holds, Common Merganser in Colorado is projected to rise about 12% by 2029 — from 0.31 in 2024 to a central estimate of 0.34 (95% range 0.10–0.59). A 5-year backtest shows a typical error of ±22%, with 100% of held-out values landing inside the 95% band.

+12%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 →
0.34Projected 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 →
0.10–0.5995% 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 →
±22%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 Colorado is projected to rise about 12% by 2029 — from 0.31 in 2024 to a central estimate of 0.34 (95% range 0.10–0.59). A 5-year backtest shows a typical error of ±22%, with 100% of held-out values landing inside the 95% band.19712029
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 →
20250.340.090.58
20260.340.090.58
20270.340.100.58
20280.340.100.59
20290.340.100.59

Common Merganser Survey Routes in Colorado

Routes recording Common Merganser in Colorado.
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 →
Tincup1220241994
Cochetopa Pass920241999
Walden720231990
Rio Grnds Rs520241991
Paonia420142002
Parlin320231981
Dolores Riv320181991
South Fork320231994
Groundhog Rs320161997
Fox Creek320231993
Gold Hill320122005
Maybell220032000
Yampa220182009
Buford220241971
Lost Lake220231994
Tarryall220231995
Guffey220181990
Animas219981998
Angora220122012
Yellowjacket Pass220012001
Lake City 2220232016
Cortez220071988
San Luis220242024
Harmony120211982
Aspen120131995

Common Merganser Population Trend in Other States

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

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