Common Merganser
Common Merganser has surged: up 14× on the route-weighted index since 1968.
About the Common Merganser
The Common Merganser (Mergus merganser) 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 739 Breeding Bird Survey routes across 29 states, most concentrated in the Northern Rockies.
- Family
- Anatidae · Waterfowl
Notable Common Merganser Trends
No notable trend signals for Common Merganser. See the full index history below.
Common Merganser Population Forecast
If the recent trend holds, Common Merganser is projected to rise about 79% by 2029 — from 0.09 in 2024 to a central estimate of 0.16 (95% range 0.09–0.23). A 5-year backtest shows a typical error of ±73.8%, with 20% of held-out values landing inside the 95% band.
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2025 | 0.15 | 0.08 | 0.23 |
| 2026 | 0.16 | 0.08 | 0.23 |
| 2027 | 0.16 | 0.09 | 0.23 |
| 2028 | 0.16 | 0.09 | 0.23 |
| 2029 | 0.16 | 0.09 | 0.23 |
Where the Common Merganser Is Detected
BBS routes recording Common Merganser, sized by most recent count.
Common Merganser Population Trend by State
| Alaska | -87% | 1983 | 52 |
| Arizona | insufficient data | n/a | 1 |
| California | -53% | 1970 | 68 |
| Colorado | +232% | 1980 | 44 |
| Connecticut | -15% | 1992 | 7 |
| Idaho | -67% | 1973 | 31 |
| Maine | +67% | 1976 | 42 |
| Maryland | insufficient data | n/a | 3 |
| Massachusetts | -8% | 2002 | 6 |
| Michigan | -18% | 1981 | 26 |
| Minnesota | -16% | 1983 | 21 |
| Montana | +313% | 1975 | 44 |
| Nevada | +9% | 1991 | 5 |
| New Hampshire | +130% | 1976 | 12 |
| New Jersey | -1% | 1991 | 6 |
| New Mexico | insufficient data | n/a | 3 |
| New York | +379% | 1969 | 61 |
| North Dakota | insufficient data | n/a | 1 |
| Ohio | insufficient data | n/a | 1 |
| Oregon | -28% | 1971 | 64 |
| Pennsylvania | +935% | 1978 | 54 |
| South Dakota | insufficient data | n/a | 2 |
| Utah | -38% | 1995 | 9 |
| Vermont | +202% | 1977 | 18 |
| Virginia | insufficient data | n/a | 6 |
| Washington | -3% | 1971 | 53 |
| West Virginia | insufficient data | n/a | 13 |
| Wisconsin | +137% | 1972 | 27 |
| Wyoming | +51% | 1977 | 59 |
Common Merganser Population Trend by Region
Bird Conservation Regions are the ecological unit for trends.
| BCR 2 | -79% | 1994 | 10 |
| BCR 4 | +320% | 1987 | 19 |
| Northern Pacific Rainforest | -45% | 1970 | 107 |
| Great Basin | +42% | 1971 | 59 |
| Northern Rockies | +99% | 1970 | 120 |
| Boreal Hardwood Transition | +113% | 1973 | 63 |
| Lower Great Lakes / St. Lawrence Plain | -6% | 1989 | 27 |
| Atlantic Northern Forest | +168% | 1969 | 90 |
| Sierra Nevada | +84% | 1972 | 17 |
| Southern Rockies / Colorado Plateau | +235% | 1975 | 54 |
| Badlands and Prairies | +12% | 1979 | 23 |
| Prairie Hardwood Transition | +76% | 1979 | 9 |
| Appalachian Mountains | 19× | 1977 | 99 |
| New England / Mid-Atlantic Coast | -60% | 1992 | 8 |
| Coastal California | -29% | 1978 | 22 |
Common Merganser Conservation Status
Our route-weighted index shows it up about 1312% since 1968.
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.