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Bonaparte's gull

Larus philadelphia

What do they look like?

Bonaparte's gulls are slate-gray headed with a very small black bill and bright orange-red legs and feet. They have a white terminal band on tail feathers and secondaries. In young birds, the wing has a dark-bordered appearance, with flashy white wing tips. Adults reach 43 to 53 cm in body length. (Pough 1953)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    200 to 250 g
    7.05 to 8.81 oz
  • Range length
    43 to 53 cm
    16.93 to 20.87 in

Where do they live?

Larus philadelphia breeds in western Canada and Alaska from July to October. Bonaparte's gulls migrate south to spend the winter on the Pacific coast from Vancouver Island to points southward. Some migrate southward as far as Panama. They sometimes occur as vagrants in in a number of European countries as well as Japan, Israel, and Morroco. (Peterson, 1980; UNEP World Conservation Monitoring Center, 2001)

What kind of habitat do they need?

Bonaparte's gulls are found in ocean bays, coastal waters, islands, and lakes. (Miklos, 1994)

  • Aquatic Biomes
  • lakes and ponds
  • coastal

How do they reproduce?

Bonaparte's gulls nest in loose colonies throughout most of Canada, from Manitoba to west-central Ontario and north to Alaska. They are the only gull species that nests almost exclusively in nests built in trees, rather than on the ground. They lay two to four eggs in nests built from twigs and moss in spruce or tamarack trees near water. The eggs are grayish to greenish brown, marked with dark brown and lilac and 4.8 by 3.3 cm on average. (Peterson, 1980)

  • How often does reproduction occur?
    Bonaparte's gulls breed once yearly.
  • Breeding season
    Bonaparte's gulls breed from July to October each year.
  • Range eggs per season
    2 to 4

How do they behave?

Bonaparte's gulls fly buoyantly and ternlike, with the bill held down. They are very active on the wing. Along the coast, where they are more abundant in fall, they feed offshore over tide channels and rips and kelp beds. They feed largely by dipping to the surface of the water. However, occasionally they drop into the water, take a few deep strokes, then glide to the surface to flutter in one spot for a moment before taking off again (Reed 1915).

How do they communicate with each other?

The vocalizations of Bonaparte's gulls can be described as a harsh high pitched see-whee and a low pitched kuk-kuk-kuk. They produce many conversational whistled notes when feeding.

What do they eat?

Small fish, crustacea, snails and marine worms are staple foods of Larus philadelphia along the coast. However, inland in summer they feed chiefly on insects they capture in the air, pick from croplands, or gather from the surface of lakes or ponds. (Miklos 1994).

Do they cause problems?

There are no adverse affects of Bonaparte's gulls on humans.

How do they interact with us?

Bonaparte's gulls are beneficial to agriculture, destroying insect pests, grubs, and worms in the fields.

  • Ways that people benefit from these animals:
  • controls pest population

Are they endangered?

The global population of Bonaparte's gulls is estimated to be between 260,000 and 530,000. This number seems to be stable.

Some more information...

Bonaparte's gulls are named after a nephew of Napoleon, Charles Lucien Bonaparte, who was a leading ornithologist in the 1800's in America and Europe. (Miklos, 1994)


Sam Park (author), University of California, Irvine, Rudi Berkelhamer (editor), University of California, Irvine.


Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

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living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

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living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

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living in the southern part of the New World. In other words, Central and South America.

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Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.


living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map


uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.


uses smells or other chemicals to communicate


the nearshore aquatic habitats near a coast, or shoreline.

  1. active during the day, 2. lasting for one day.

animals that generate their own body heat through metabolic processes.


an area where a freshwater river meets the ocean and the fresh and saltwater mixes


mainly lives in water that is not salty.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


makes seasonal movements between breeding and wintering grounds


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season


reproduction that includes combining the genetic contribution of two individuals, a male and a female


uses touch to communicate


that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).


uses sight to communicate


Burger, J., M. Gochfeld. 2002. Bonaparte's gull (Larus philadelphia). Pp. 1-24 in A Poole, F Gill, eds. The Birds of North America, Vol. 634. Philadelphia, PA: The Birds of North America, Inc.

Miklos, D. 1994. National Audubon Society Field Guide to North American Birds. New York: Alfred A. Knopf, inc..

Peterson, R. 1980. A Field Guide to the Birds. Boston: Houghton Mifflin Company.

Pough, R. 1953. All the Birds of Eastern and Central North America. New York: Doubleday & Company,inc..

Reed, C. 1915. The Bird Book. New York: Doubleday, page & Company.

UNEP World Conservation Monitoring Center, 2001. "Threatened and Endangered Species: Larus philadelphia" (On-line). Accessed 2 March 2001 at

University of Michigan Museum of ZoologyNational Science Foundation

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Park, S. 2001. "Larus philadelphia" (On-line), Animal Diversity Web. Accessed April 25, 2014 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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