Larus delawarensisring-billed gull

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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. (Farrand, 1988; Palmer and Fowler, 1975)

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. (Farrand, 1988; Palmer and Fowler, 1975; Ryder, 1993)

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

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. (Farrand, 1988; Palmer and Fowler, 1975; Peterson, 1967)

  • Sexual Dimorphism
  • male larger
  • Range mass
    300 to 700 g
    10.57 to 24.67 oz
  • Range length
    43 to 54 cm
    16.93 to 21.26 in
  • Average wingspan
    127 cm
    50.00 in
  • Average basal metabolic rate
    2.91742 W
    AnAge

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. (Ryder, 1993)

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. (Farrand, 1988; Palmer and Fowler, 1975; Ryder, 1993)

  • Breeding interval
    Ring-billed gulls breed once per year.
  • Breeding season
    Ring-billed gulls breed between May and August.
  • Range eggs per season
    2 to 4
  • Average eggs per season
    3
    AnAge
  • Range time to hatching
    20 to 31 days

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
  • 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.

  • Range lifespan
    Status: wild
    23 (high) years
  • Typical lifespan
    Status: wild
    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. (Farrand, 1988; Palmer and Fowler, 1975; Ryder, 1993)

  • Range territory size
    1 to 5 m^2

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. (Ryder, 1993)

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. (Farrand, 1988; Palmer and Fowler, 1975; Ryder, 1993)

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. (Farrand, 1988; Fisher and Chartier, 1997; Palmer and Fowler, 1975)

  • 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. (Ryder, 1993)

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. (Ryder, 1993)

Economic Importance for Humans: Positive

Ring-billed gulls often eat garbage created by humans, which helps reduce waste. (Farrand, 1988; Palmer and Fowler, 1975)

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.

Contributors

Tanya Dewey (author), Animal Diversity Web.

Kari Kirschbaum (editor), Animal Diversity Web.

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

Glossary

Nearctic

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.

World Map

Neotropical

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

World Map

acoustic

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. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

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

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

freshwater

mainly lives in water that is not salty.

iteroparous

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).

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

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

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

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

polygynous

having more than one female as a mate at one time

saltwater or marine

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

seasonal breeding

breeding is confined to a particular season

sexual

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

social

associates with others of its species; forms social groups.

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

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).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

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 A Poole, P Stettenheim, F Gill, eds. The Birds of North America, Vol. 33. Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.