[order] CHARADRIIFORMES | [family] Laridae | [latin] Larus delawarensis | [UK] Ring-billed Gull | [FR] Goeland a bec cercle | [DE] Ringschnabel-Mowe | [ES] | [NL] Ringsnavelmeeuw
Subspecies
Monotypic species
Physical charateristics
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.
Listen to the sound of Ring-billed Gull
[audio:http://www.aviflevoland.nl/sounddb/R/Ring-billed Gull.mp3]
Copyright remark: Most sounds derived from xeno-canto
| wingspan min.: | 125 | cm | wingspan max.: | 130 | cm |
| size min.: | 50 | cm | size max.: | 56 | cm |
| incubation min.: | 20 | days | incubation max.: | 31 | days |
| fledging min.: | 4 | days | fledging max.: | 31 | days |
| broods: | 1 | eggs min.: | 2 | ||
| eggs max.: | 4 |
Range
North America, Middle America : widespread
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.
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.
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 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.
Feeding 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.
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.
Conservation
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be increasing, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Migration
Wanders N to Alaska and Yukon. Winters from S part of breeding range S to Greater Antilles; becoming commoner in Central America, both in the interior and along coasts; also occurs increasingly in Lesser Antilles; first recorded in Florida in 1930, now common in winter. E population migrates to Atlantic coast and S to Gulf Coast, few reaching West Indies and Central America. Birds of plains and mountain states move to pacific coast. Large numbers remain on Great Lakes until freeze-up. Most Great Lakes birds return to the lake where they hatched, but not necessarily to same colony. Since mid-1970’s has become regular vagrant to W Palearctic (see page 595), especially in British Is, where records span all months of the year; massive influx of over 400 individuals in first half of 1980’s has led to species becoming a virtual resident in some coastal areas.
Distribution map
