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Photo by Donna Dewhurst
Photo Courtesy of U. S. Fish and Wildlife Service
Bonaparte's Gull
Chroicocephalus philadelphia
NatureServe conservation status
Global (G-rank): G5
State (S-rank): SNA
External links
General information
Bonaparte's gull, Larus philadelphia, spends the summer breeding season in coniferous woodlands near ponds and lakes in Alaska and Canada. It winters along both the east and west coasts of the United States, and in the Great Lakes region. Bonaparte's gull is a widespread migrant in localized areas of the inland United States. Individuals and small flocks of transient Bonaparte's gulls have been spotted throughout Utah, though they are uncommon in the state.
The diet of Bonaparte's gull consists primarily of aquatic insects that are picked off the surface of the water, although Bonaparte's gulls will also dive into the water from great heights to capture fishes and other aquatic animals. It is believed that a mating pair finds an abandoned tree nest and lines it with a soft material. Three eggs are then laid and incubated for about twenty-four days. The young, which are fed by their parents until they leave the nest, attain their adult plumage after two years.
Species range
BREEDING: western and central Alaska, central Yukon, northwestern and central Mackenzie, and northern Manitoba south to base of Alaska Peninsula, south-coastal and (rarely) southeastern Alaska, southern British Columbia, southwestern Alberta, central Saskatchewan, southern Manitoba, and central Ontario. Nonbreeders occur in summer south along coast to California and New England, and in interior to Great Lakes. NON-BREEDING: from Washington south along coast to northwestern Mexico (southern Baja California, Sinaloa); Great Lakes; southeastern Canada south along coast to Florida, west to southern Texas and central Mexico; Bermuda, Bahamas, and Greater Antilles; occasional in Hawaii (AOU 1983, NGS 1983, Sibley and Monroe 1990).
Migration
Migrates most commonly through eastern North America from Mississippi Valley east to Appalachians (AOU 1983). In fall, uses 3 flyways: the Pacific, Mississippi, and Atlantic, with the majority (60%) following the Mississippi Flyway from the Great Lakes to the Gulf of Mexico, and the remainder of the population split between the two coasts (21% Atlantic, 19% Pacific) (Braune 1989). Main fall routes through Atlantic Flyway: Saguenay River-Upper Saint John River-St. Croix River-Quoddy region, southwestern Bay of Fundy; Lower Great Lakes-Mohawk River-Hudson River-Long Island, New York area; Lower Great Lakes-Delaware River-Delaware Bay/Chesapeake Bay (Braune 1989). By late July, flocks of breeding birds form on larger boreal lakes prior to fall migration (Johnson and Herter 1989). Fall migration tends to be more coastal than does spring migration.
Habitat
NON-BREEDING: along seacoasts, bays and harbors, estuaries, mudflats, marshes, rivers, lakes, ponds, and flooded fields (AOU 1983). More pelagic than most gulls, often feeds offshore (Braune 1989). BREEDING: coniferous woodland near ponds and lakes. Often nests in trees in old bird's nest (AOU 1983).
Food habits
Feeds primarily on insects and fishes in lakes and bays; also eats crustaceans and marine worms and scavenges (Bent 1921). July-December diet off New Brunswick: fishes, euphausiids, insects, polychaetes, amphipods; opportunistic feeder (Braune 1987). Young are fed insects gleaned from water surface or from water plants (Johnson and Herter 1989). Feeds on insects and marine invertebrates frequently in areas where prey concentrated by currents, waterfalls, glaciers, and other natural features (see Johnson and Herter 1989).
Ecology
Nonbreeding: often seen in loose flocks; often associates with terns when feeding or resting.
Reproductive characteristics
Breeding begins mid-June (Harrison 1978). Incubates 2-3, usually 3, eggs for 24 days (Terres 1980). Nestlings are semi-precocial and downy. Usually nests solitarily or in small groups (Terres 1980).
References
- Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1988. The birder’s handbook[:] a field guide to the natural history of North American birds. Simon & Schuster, New York. xxx + 785 pp.
- National Geographic Society. 1996. Field guide to the birds of North America, 2nd edition. The National Geographic Society, Washington, D. C.
- Behle, W. H., Sorensen, E. D. and C. M. White. 1985. Utah birds: a revised checklist. Utah Museum of Natural History, Occasional Publication No. 4. Salt Lake City, UT.
