BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Red-breasted Merganser

AnatidaeWaterfowlMergus serrator

Red-breasted Merganser has surged: up 84% on the route-weighted index since 1969.

+84%Since 1969TrendPercent 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 →
64RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
57Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

About the Red-breasted Merganser

The Red-breasted Merganser (Mergus serrator) is a North American member of the Ducks, Geese & Waterfowl (Anatidae). In this analysis it is grouped with the waterfowl.

Size
12–43.5 in long (30–110 cm) — a medium to large waterfowl (typical for the family)
Habitat
Lakes, ponds, rivers, marshes and sheltered coastal waters.
Diet
Aquatic plants, seeds and invertebrates, dabbled at the surface or dived for.
Range
Recorded on 64 Breeding Bird Survey routes across 5 states, most concentrated in the BCR 2.
Family
Anatidae · Waterfowl

Notable Red-breasted Merganser TrendsNotable 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 Red-breasted Merganser. See the full index history below.

Red-breasted Merganser Population Forecast

If the recent trend holds, Red-breasted Merganser is projected to stay roughly flat through 2029, near 0.04 (95% range 0.01–0.08). A 5-year backtest shows a typical error of ±139.8%, with 100% of held-out values landing inside the 95% band.

n/aChange 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 →
0.01–0.0895% 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 →
±139.8%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, Red-breasted Merganser is projected to stay roughly flat through 2029, near 0.04 (95% range 0.01–0.08). A 5-year backtest shows a typical error of ±139.8%, 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 →
20250.040.010.08
20260.040.010.08
20270.040.010.08
20280.040.010.08
20290.040.010.08

Where the Red-breasted Merganser Is Detected

BBS routes recording Red-breasted Merganser, sized by most recent count.

Red-breasted Merganser Population Trend by State

Red-breasted Merganser population trend by state.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Alaska-42%198547
Maineinsufficient datan/a2
Michiganinsufficient datan/a6
Minnesota-27%19765
Wisconsin-90%19694

Red-breasted Merganser Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Red-breasted Merganser population trend by Bird Conservation Region.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
BCR 2-69%198518
BCR 4+382%199116
Northern Pacific Rainforest-53%19919
Boreal Hardwood Transition-87%196913

Red-breasted Merganser Conservation Status

Our route-weighted index shows it up about 84% since 1969.

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.