Larus delawarensis

Geographic Range

Ring-billed gulls range from southern Alaska to the north shore of the Gulf of St. Lawrence, to southern parts of Oregon and Colorado and northern New York. During the winter, it is found from British Columbia to Maine (including the Great Lakes and Maritime regions), then south to central California to southern Mexico to the Gulf Coast to Cuba. It is also found in Bermuda and Hawaii. This gull winters from southwestern British Columbia and Washington state to the Great Lakes region to Nova Scotia then southward.

• Biogeographic Regions
• nearctic nearctic
  • native native
• neotropical neotropical
  • native native

Habitat

These birds frequent inland waterways. They may be found in areas with sandy ground where vegetation is sparse. They may also be found where there are rocks and concrete pieces, on pebble beaches, and sometimes in wet meadows. Their preference for open areas makes them well-suited to urban and suburban landscapes and they are often found on large, grassy lawns, parking lots, and in vacant land.

In western areas of the U.S., Ring-billed gull colonies tend to be found within a 36 km radius of small towns or agricultural areas. This is not necessarily the case in the eastern U.S. where their main food is fish.

• Habitat Regions
• temperate temperate
• saltwater or marine saltwater or marine
• freshwater freshwater

• Terrestrial Biomes
• desert or dune desert or dune

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• coastal coastal

• Other Habitat Features
• urban urban
• suburban suburban

Physical Description

Ring-billed gulls are medium-sized gulls. Males are larger than females. They are 46 to 54 cm long (average 50.2 cm) and weigh 400 to 700 g (average 550 g). Females are 43 to 50 cm long (average 46.9 cm) and weigh 300 to 600 g (average 470 g). Adults of both sexes have a wingspan of approximately 127 cm.

The back and shoulders of ring-billed gulls are pale bluish-gray, and the head is white. The wings are tipped in black with evident white spots, and the belly is whitish.

Ring-billed gulls have yellowish or greenish legs and feet. Their most distinctive feature is a sharply defined narrow black band that encircles the bill.

Immature ring-billed gulls have different coloration than adults. First year birds are whitish with brown flecks and have very dark wing tips and tails. Second year birds are more like the adults, but have a black-tipped tail.

Chicks have two color phases; some are smoky gray, while others are buff with dark spots.

Ring-billed gulls may be confused with herring gulls ( Larus argentatus ). Herring gulls are larger and have a thicker bill that lacks a clearly defined black ring.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Ring-billed gulls are generally monogamous. Breeding pairs form immediately before or during arrival on the breeding grounds and territory establishment. In expanding colonies, polygynous trios (two females attending the same nest and mated to the same male) are frequently observed.

• Mating System
• monogamous monogamous
• polygynous polygynous

Ring-billed gulls nest in colonies on the ground, or infrequently, in trees near inland lakes. Nests are built by both members of a breeding pair. Nests are constructed of dead plant material including twigs, sticks, grasses, leaves, lichens and mosses, and may be interspersed with those of other water birds.

The female lays 2 to 4 (usually 3) eggs per clutch, each about 6.4 cm long by 4.6 cm wide. The eggs are light blue, green or brownish and spotted. Both male and female incubate the eggs. The semiprecocial chicks hatch after 20 to 31 days, and are brooded and fed by both parents. The chicks begin leaving the nest within days of hatching, and are able to fly at about 5 weeks old.

Ring-billed gulls breed between May and August. The age at first breeding is not known, but is probably at least two years.

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

Both parents incubate the eggs and feed nestlings until they reach independence. The young remain in the nest until they are able to walk, at about 4 days old. Birds depart from the nesting area immediately upon fledging, at about 45 days old.

• Parental Investment
• precocial precocial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • protecting
    • male
    • female
• pre-weaning/fledging
  • provisioning
    • male
    • female
  • protecting
    • male
    • female
• pre-independence
  • provisioning
    • male
    • female

Lifespan/Longevity

Ring-billed gulls have been recorded living as long as 23 years in the wild. However, it is likely that the majority of these birds live much shorter lives than this, probably 3 to 10 years.

Behavior

Ring-billed gulls are diurnal and migratory. They are also highly social, occupying large colonies especially during the breeding season. They defend small territories within nesting colonies. They engage in play, dropping objects while airborne, then swooping down to catch them. They may steal food from other gulls and European starlings as well as fending off other birds that may steal their food.

• Key Behaviors
• terricolous
• flies
• diurnal diurnal
• motile motile
• migratory migratory
• territorial territorial
• social social
• colonial colonial

Home Range

There is no information on the home range of ring-billed gulls. In one study, 69% of banded ring-billed gulls returned to their natal colony to nest, and 90% returned to a colony where they had nested previously.

Communication and Perception

Ring-billed Gulls primarily communicate using calls and body language. They have two alert calls; a screeching call that sounds like "kree, kree" and a shrill "kyow kyow kyow " call that sounds high-pitched and squealing. A "mew" call is used during courtship feeding, feeding of chicks, and other non-aggressive types of behavior. The long call is given during hostile displays and landing.

While engaging in aggressive behaviors, ring-billed gulls lower their head to their feet, then toss their head backward before ending a long call. During submissive displays, they draw in their head and neck in a hunched fashion, sounding short, high-pitched "klioo" notes and engaging in head tossing.

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Ring-billed gulls are opportunistic feeders, or scavengers, meaning they will eat almost anything that they find. They eat fish , rodents , small aquatic animals, bird chicks and eggs , insects , and vegetable matter such as fruits, though they prefer animal foods.

This kind of feeding behavior has made them very successful in areas around humans where they take advantage of land fills, garbage dumps, and ships that dump garbage overboard. They also scavenge from plowed fields, parks, and parking lots. In fact, these gulls might be seen squabbling over discarded items from fast-food restaurants. Ring-billed gulls are able to snatch food from the water's surface while in flight.

• Primary Diet
• omnivore omnivore

• Animal Foods
• birds
• mammals
• fish
• insects
• terrestrial worms

• Plant Foods
• seeds, grains, and nuts
• fruit

Predation

Predators of ring-billed gull adults, chicks and eggs include red fox , coyote , striped skunk , raccoons , long-tailed weasel , mink , California gulls , herring gulls , great horned owls , snowy owls , American crows and common ravens .

Ring-billed gulls respond to predators by swooping and soaring above them, and mobbing them in small groups. Because ring-billed gulls nest and feed in large colonies they rely on each other to detect predators. The alarm calls and panic flights of colony members alert others to the presence of predators.

Ecosystem Roles

Ring-billed Gulls are scavengers, so they often consume foods that would otherwise go to waste. They affect the populations of the animals they prey upon. They also support the populations of small predators that prey on them.

Ring-billed gulls compete with other gull species for food and have been observed stealing food from starlings .

Economic Importance for Humans: Positive

Ring-billed gulls often eat garbage created by humans, which helps reduce waste.

Economic Importance for Humans: Negative

Some people consider large groups of these birds to be pests due to their droppings, garbage stealing, and the noise that they create.

Conservation Status

Ring-billed Gull populations are not threatened. Population sizes may have increased in recent historical times because ring-billed gulls benefit from human activities, such as landfills and fishing practices.

They are protected under the U.S. Migratory Bird Treaty Act as migratory birds.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Tanya Dewey (author), Animal Diversity Web.

Kari Kirschbaum (editor), Animal Diversity Web.

Janice Pappas (author), University of Michigan-Ann Arbor.

References

Farrand, J. 1988. Eastern Birds; An Audubon Handbook . New York: McGraw-Hill, Inc.

Fisher, C., A. Chartier. 1997. Birds of Detroit . Canada: Lone Pine Publishing.

Palmer, E., H. Fowler. 1975. Fieldbook of Natural History, 2nd ed . New York: McGraw-Hill, Inc.

Peterson, R. 1967. A Field Guide to the Birds: Eastern Land and Water Birds, 2nd ed . Boston: Houghton Mifflin Company.

Ryder, J. 1993. Ring-billed Gull. Pp. 1-28 in The Birds of North America , Vol. 33. Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.