Species · California · BBS 2025 Release · 1966–2024
Forster's Tern Population Trend in California
Forster's Tern in California has fallen sharply: down 60% on the route-weighted index since 1970.
-60%Since 1970
34Routes In State
54Years
Notable Forster's Tern Trends in California
long arc declinecomputed index
Forster's Tern has fallen sharply in California: down 60% on the route-weighted index since 1970.
Forster's Tern Population Forecast in California
If the recent trend holds, Forster's Tern in California is projected to stay roughly flat through 2029, near 0.69 (95% range 0.00–1.6). A 5-year backtest shows a typical error of ±1365.3%, with 40% of held-out values landing inside the 95% band.
n/aChange by 2029
0.69Projected 2029 index
0.00–1.695% range
±1365.3%Backtest error
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2025 | 0.69 | 0.00 | 1.6 |
| 2026 | 0.69 | 0.00 | 1.6 |
| 2027 | 0.69 | 0.00 | 1.6 |
| 2028 | 0.69 | 0.00 | 1.6 |
| 2029 | 0.69 | 0.00 | 1.6 |
Forster's Tern Survey Routes in California
| Dorris | 68 | 2019 | 1972 |
| Oroville | 30 | 2013 | 1973 |
| Poway | 21 | 1978 | 1973 |
| Carrizo Pln | 15 | 1991 | 1991 |
| Collegeville | 8 | 1987 | 1987 |
| Macdoel | 7 | 2018 | 1972 |
| Fairfax | 6 | 1991 | 1974 |
| Sattley | 5 | 2016 | 1990 |
| Iron Gate | 4 | 2002 | 1988 |
| Redding | 4 | 1975 | 1975 |
| Copperopolis | 4 | 2001 | 1980 |
| Crowder Flat | 3 | 2006 | 2002 |
| Crowley Lake | 2 | 1988 | 1988 |
| Foster Park | 2 | 1990 | 1990 |
| Cedarville | 2 | 2014 | 1977 |
| Hollister | 2 | 2003 | 1992 |
| Coyote | 2 | 2014 | 1974 |
| Ingalls | 2 | 2001 | 1974 |
| Nubieber | 1 | 2014 | 1980 |
| Eagle Lake | 1 | 2007 | 1972 |
| Hughson | 1 | 2024 | 1968 |
| Glenn | 1 | 1983 | 1982 |
| Cordova | 1 | 1981 | 1981 |
| Madeline | 1 | 2024 | 2015 |
| Westley | 1 | 2003 | 1989 |
Forster's Tern Population Trend in Other States
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.