Species · Delaware · BBS 2025 Release · 1966–2024
Common Tern Population Trend in Delaware
Common Tern in Delaware has collapsed: down 90% on the route-weighted index since 1968.
-90%Since 1968
5Routes In State
21Years
Notable Common Tern Trends in Delaware
long arc declinecomputed index
Common Tern has collapsed in Delaware: down 90% on the route-weighted index since 1968.
Common Tern Population Forecast in Delaware
If the recent trend holds, Common Tern in Delaware is projected to fall about 100% by 2019 — from 0.14 in 2014 to a central estimate of 0.00 (95% range 0.00–6.6). A 5-year backtest shows a typical error of ±1378%, with 80% of held-out values landing inside the 95% band.
-100%Change by 2019
0.00Projected 2019 index
0.00–6.695% range
±1378%Backtest error
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2015 | 0.00 | 0.00 | 6.6 |
| 2016 | 0.00 | 0.00 | 6.6 |
| 2017 | 0.00 | 0.00 | 6.6 |
| 2018 | 0.00 | 0.00 | 6.6 |
| 2019 | 0.00 | 0.00 | 6.6 |
Common Tern Survey Routes in Delaware
| Milton | 6 | 1975 | 1971 |
| Lowes Xrds | 3 | 1991 | 1966 |
| Bethany Bch | 2 | 1990 | 1966 |
| Dover | 1 | 1977 | 1977 |
| Blackbird | 1 | 2014 | 2014 |
Common Tern Population Trend in Other States
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.