Species · California · BBS 2025 Release · 1966–2024
Common Merganser Population Trend in California
Common Merganser in California has fallen sharply: down 53% on the route-weighted index since 1970.
-53%Since 1970
68Routes In State
56Years
Notable Common Merganser Trends in California
long arc declinecomputed index
Common Merganser has fallen sharply in California: down 53% on the route-weighted index since 1970.
Common Merganser Population Forecast in California
If the recent trend holds, Common Merganser in California is projected to stay roughly flat through 2029, near 0.47 (95% range 0.14–0.80). A 5-year backtest shows a typical error of ±638%, with 60% of held-out values landing inside the 95% band.
n/aChange by 2029
0.47Projected 2029 index
0.14–0.8095% range
±638%Backtest error
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2025 | 0.46 | 0.12 | 0.79 |
| 2026 | 0.46 | 0.13 | 0.79 |
| 2027 | 0.46 | 0.13 | 0.79 |
| 2028 | 0.46 | 0.13 | 0.80 |
| 2029 | 0.47 | 0.14 | 0.80 |
Common Merganser Survey Routes in California
| Iron Gate | 24 | 2019 | 1988 |
| Alderpoint | 18 | 2006 | 1975 |
| Horse Creek | 15 | 2019 | 1970 |
| Longvale | 7 | 2023 | 1972 |
| Genesee | 6 | 2023 | 1985 |
| Junction Cty | 5 | 2012 | 1972 |
| Copperopolis | 5 | 2021 | 1989 |
| Riverton | 4 | 2017 | 1980 |
| Bodega Bay | 4 | 2021 | 1981 |
| Eagle Lake | 3 | 2023 | 1969 |
| Likely | 3 | 1999 | 1985 |
| Chilcoot | 3 | 2023 | 1998 |
| Shasta Lake | 3 | 2007 | 1973 |
| Woodfords | 3 | 2022 | 1986 |
| Holmes | 2 | 2022 | 1968 |
| Redwood N.P. | 2 | 2006 | 1996 |
| Hiouchi | 2 | 2003 | 2003 |
| Whiskeytown | 2 | 2007 | 2002 |
| Tomhead | 2 | 2005 | 2005 |
| Meadow Valley | 2 | 2023 | 2018 |
| Little Truckee | 2 | 2017 | 2013 |
| Lockwood | 2 | 2024 | 1984 |
| Clear Lk Res | 2 | 2004 | 2004 |
| Korbel | 2 | 1981 | 1979 |
| Ono | 2 | 2012 | 2002 |
Common Merganser Population Trend in Other States
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.