Bonaparte's Gull
Chroicocephalus philadelphia

Conservation status | Numbers apparently stable. Has not benefitted from human activities as much as some gulls (e.g., does not feed at dumps). However, most of its nesting areas are remote from human disturbance. |
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Family | Gulls and Terns |
Habitat | Ocean bays, lakes, muskeg. Breeds in edges of northern forest, where coniferous trees are near lakes or bogs. In migration and winter on many kinds of waters, including rivers and lakes inland, coastal estuaries and lagoons, sometimes well offshore on ocean. Often concentrates at sewage treatment ponds, probably to feed on the abundant insects there. |
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Feeding Behavior
Forages in flight by plunging into the water or dipping to the surface; also picks up items while swimming or wading. Often catches insects in the air. Unlike larger gulls, seldom scavenges at carrion or garbage dumps.
Eggs
3, sometimes 2 or 4. Olive to buff, blotched with brown. Incubation is probably by both parents, about 24 days. Young: Both parents feed young in nest. Development of young and age at first flight not well known. If intruders approach the nest, the adults perch on nearby treetops or fly about calling in protest.
Young
Both parents feed young in nest. Development of young and age at first flight not well known. If intruders approach the nest, the adults perch on nearby treetops or fly about calling in protest.
Diet
Insects, crustaceans, fish. Around inland nesting areas, apparently feeds mostly on insects. In coastal regions, where it spends most of the year, diet includes small fish (such as sand lance, herring, and pollock), crustaceans (especially euphausiid shrimp), insects, marine worms, and other invertebrates.
Nesting
Breeding behavior is not well known. Nests in isolated pairs or small colonies in sparse northern forest near water. Nest site is in coniferous tree, on horizontal branch usually 4-15' above ground, sometimes up to 20' or higher. Sometimes may build nest on ground. Nest is usually a rather small platform or open cup of sticks, lined with finer materials such as grass and moss.
Illustration © David Allen Sibley.
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Text © Kenn Kaufman, adapted from
Lives of North American Birds
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Migration
Many birds from central Canada apparently move east or west toward nearest coast in fall. In winter, flocks may move around a lot in response to changing food supplies.

- All Seasons - Common
- All Seasons - Uncommon
- Breeding - Common
- Breeding - Uncommon
- Winter - Common
- Winter - Uncommon
- Migration - Common
- Migration - Uncommon
See a fully interactive migration map for this species on the Bird Migration Explorer.
Learn moreSongs and Calls
Rasping tee-ar; soft, nasal snarling note.Learn more about this sound collection.
How Climate Change Will Reshape the Range of the Bonaparte's Gull
Audubon’s scientists have used 140 million bird observations and sophisticated climate models to project how climate change will affect this bird’s range in the future.
Zoom in to see how this species’s current range will shift, expand, and contract under increased global temperatures.
Climate threats facing the Bonaparte's Gull
Choose a temperature scenario below to see which threats will affect this species as warming increases. The same climate change-driven threats that put birds at risk will affect other wildlife and people, too.