Critter Catalog

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)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

• 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)

• Biogeographic Regions
• nearctic
  • native
• palearctic
  • native
• ethiopian
  • native
• neotropical
  • native
• atlantic ocean
  • native
• pacific ocean
  • native

What kind of habitat do they need?

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

• These animals are found in the following types of habitat
• temperate
• saltwater or marine
• freshwater

• Aquatic Biomes
• lakes and ponds
• coastal

• Other Habitat Features
• estuarine

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)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• oviparous

• 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).

• Key Behaviors
• flies
• natatorial
• diurnal
• motile
• migratory

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.

• Communication Channels
• visual
• acoustic

• Perception Channels
• visual
• tactile
• acoustic
• chemical

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.

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Migratory Bird Act

  Protected

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

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)

Contributors

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

References

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 http://www.unep-wcmc.org/?http://ims.wcmc.org.uk/isdb/Taxonomy/tax-species-result.cfm?Genus=Larus&Species=philadelphia~main.