Bonaparte's Gull
Bonaparte's Gull has declined: down 34% on the route-weighted index since 1982.
About the Bonaparte's Gull
The Bonaparte's Gull (Chroicocephalus philadelphia) is a North American member of the Gulls, Terns & Skimmers (Laridae). In this analysis it is grouped with the wetland birds.
- Size
- 8.5–31.5 in long (22–80 cm) — a long-winged waterbird (typical for the family)
- Habitat
- Marshes, ponds, lakeshores and other freshwater wetlands.
- Diet
- Aquatic invertebrates, small fish, frogs and plant matter.
- Range
- Recorded on 62 Breeding Bird Survey routes across 6 states, most concentrated in the BCR 4.
- Family
- Laridae · Wetland birds
Notable Bonaparte's Gull Trends
No notable trend signals for Bonaparte's Gull. See the full index history below.
Bonaparte's Gull Population Forecast
If the recent trend holds, Bonaparte's Gull is projected to stay roughly flat through 2029, near 0.00 (95% range 0.00–0.07). A 5-year backtest shows a typical error of ±241.2%, with 100% of held-out values landing inside the 95% band.
| Year | Projected index | 95% low | 95% high |
|---|---|---|---|
| 2025 | 0.00 | 0.00 | 0.07 |
| 2026 | 0.00 | 0.00 | 0.07 |
| 2027 | 0.00 | 0.00 | 0.07 |
| 2028 | 0.00 | 0.00 | 0.07 |
| 2029 | 0.00 | 0.00 | 0.07 |
Where the Bonaparte's Gull Is Detected
BBS routes recording Bonaparte's Gull, sized by most recent count.
Bonaparte's Gull Population Trend by State
| Alaska | -79% | 1984 | 53 |
| California | insufficient data | n/a | 4 |
| Maine | insufficient data | n/a | 1 |
| North Dakota | insufficient data | n/a | 1 |
| Oregon | insufficient data | n/a | 1 |
| Washington | insufficient data | n/a | 2 |
Bonaparte's Gull Population Trend by Region
Bird Conservation Regions are the ecological unit for trends.
| BCR 2 | +37% | 1996 | 7 |
| BCR 4 | -71% | 1984 | 33 |
| Northern Pacific Rainforest | +619% | 1984 | 18 |
Bonaparte's Gull Conservation Status
Our route-weighted index shows it down about 34% since 1982.
Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.