Species · Delaware · BBS 2025 Release · 1966–2024
Least Tern Population Trend in Delaware
Least Tern in Delaware has collapsed: down 88% on the route-weighted index since 1968.
-88%Since 1968
7Routes In State
25Years
Notable Least Tern Trends in Delaware
long arc declinecomputed index
Least Tern has collapsed in Delaware: down 88% on the route-weighted index since 1968.
Least Tern Population Forecast in Delaware
If the recent trend holds, Least Tern in Delaware is projected to fall about 100% by 2023 — from 0.50 in 2018 to a central estimate of 0.00 (95% range 0.00–4.9). A 5-year backtest shows a typical error of ±268.9%, with 100% of held-out values landing inside the 95% band.
-100%Change by 2023
0.00Projected 2023 index
0.00–4.995% range
±268.9%Backtest error
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2019 | 0.00 | 0.00 | 4.9 |
| 2020 | 0.00 | 0.00 | 4.9 |
| 2021 | 0.00 | 0.00 | 4.9 |
| 2022 | 0.00 | 0.00 | 4.9 |
| 2023 | 0.00 | 0.00 | 4.9 |
Least Tern Survey Routes in Delaware
| Bethany Bch | 21 | 1990 | 1966 |
| Lowes Xrds | 20 | 1987 | 1968 |
| Harrington | 3 | 2018 | 1966 |
| Blackbird | 3 | 1998 | 1998 |
| Dover | 2 | 1974 | 1974 |
| Milton | 2 | 1971 | 1971 |
| Georgetown | 1 | 1994 | 1994 |
Least Tern Population Trend in Other States
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.