Species · California · BBS 2025 Release · 1966–2024
Black Tern Population Trend in California
Black Tern in California has collapsed: down 77% on the route-weighted index since 1973.
-77%Since 1973
19Routes In State
50Years
Notable Black Tern Trends in California
long arc declinecomputed index
Black Tern has collapsed in California: down 77% on the route-weighted index since 1973.
Black Tern Population Forecast in California
If the recent trend holds, Black Tern in California is projected to stay roughly flat through 2027, near 0.11 (95% range 0.00–0.31). A 5-year backtest shows a typical error of ±315.9%, with 100% of held-out values landing inside the 95% band.
n/aChange by 2027
0.11Projected 2027 index
0.00–0.3195% range
±315.9%Backtest error
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2023 | 0.12 | 0.00 | 0.31 |
| 2024 | 0.12 | 0.00 | 0.31 |
| 2025 | 0.11 | 0.00 | 0.31 |
| 2026 | 0.11 | 0.00 | 0.31 |
| 2027 | 0.11 | 0.00 | 0.31 |
Black Tern Survey Routes in California
| Ora Loma | 43 | 1973 | 1973 |
| Clear Lk Res | 13 | 2004 | 1980 |
| Sattley | 5 | 1976 | 1976 |
| Dorris | 5 | 2017 | 1976 |
| Crowder Flat | 3 | 2019 | 2002 |
| Madeline | 3 | 2022 | 1997 |
| Crowley Lake | 3 | 1982 | 1982 |
| Glenn | 2 | 2021 | 1971 |
| Macdoel | 2 | 2005 | 1972 |
| Tranquillity | 2 | 1995 | 1972 |
| Ravendale | 2 | 1979 | 1973 |
| Orland | 2 | 1996 | 1977 |
| Nubieber | 1 | 2000 | 1973 |
| Eagle Lake | 1 | 1974 | 1973 |
| Hughson | 1 | 1991 | 1991 |
| Likely | 1 | 2008 | 1972 |
| Goumaz | 1 | 2004 | 1997 |
| Honey Lake | 1 | 1994 | 1974 |
| Ingalls | 1 | 1988 | 1982 |
Black Tern Population Trend in Other States
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.