Species · Colorado · BBS 2025 Release · 1966–2024
Forster's Tern Population Trend in Colorado
Forster's Tern in Colorado has collapsed: down 77% on the route-weighted index since 1992.
-77%Since 1992
5Routes In State
19Years
Notable Forster's Tern Trends in Colorado
long arc declinecomputed index
Forster's Tern has collapsed in Colorado: down 77% on the route-weighted index since 1992.
Forster's Tern Population Forecast in Colorado
If the recent trend holds, Forster's Tern in Colorado is projected to stay roughly flat through 2021, near 0.03 (95% range 0.00–0.11). A 5-year backtest shows a typical error of ±95%, with 80% of held-out values landing inside the 95% band.
n/aChange by 2021
0.03Projected 2021 index
0.00–0.1195% range
±95%Backtest error
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2017 | 0.03 | 0.00 | 0.11 |
| 2018 | 0.03 | 0.00 | 0.11 |
| 2019 | 0.03 | 0.00 | 0.11 |
| 2020 | 0.03 | 0.00 | 0.11 |
| 2021 | 0.03 | 0.00 | 0.11 |
Forster's Tern Survey Routes in Colorado
| Neegrande | 4 | 1997 | 1997 |
| Fort Morgan | 3 | 1996 | 1996 |
| Walden | 2 | 2016 | 1990 |
| Julesburg | 1 | 2009 | 2009 |
| Haswell | 1 | 1999 | 1997 |
Forster's Tern Population Trend in Other States
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.