Ring-billed Gull

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Image:Ring-billed gull.JPG

Common Name: Ring-billed Gull
Scientific Name: Larus delawarensis

Size: 17.5 inches (44.5 cm); wingspan 48 inches (122 cm)

Habitat: North America; throughout Southern Canada, the continental United States, Mexico and Caribbean.

Ring-billed Gulls often congregate around humans, at garbage dumps, parking lots, and freshly plowed fields. While the species is common on coastal beaches, particularly during winter, many Ring-billed Gulls lead inland lives, never setting eyes on the sea.

Status: Least Concern. Global Population: 2,600,000 mature individuals. After nearly succumbing to hunting and habitat loss, Ring-billed Gulls once again thrive across the United States and southern Canada—so numerous in some places that they are considered pests. Their populations plummeted during the late nineteenth century, when humans encroached on the birds' nesting grounds and killed them for feathers to decorate hats. By the early 1900s many breeding sites were defunct. Protection under the 1917 Migratory Birds Convention Act (Canada) and 1918 Migratory Bird Treaty Act (U.S.) helped bring the species back. In the middle of the twentieth century, Ring-billed Gulls around Lake Ontario proved susceptible to the pesticide DDT and to PCB pollution. Environmental regulations in the 1970s helped reduce pollution levels. Humans have generally helped Ring-billed Gulls by providing extra foods, including introduced fish; insects and grain exposed on farm fields; and discarded food and refuse. The Ring-billed Gull continues to extend its breeding range—likely fueled in part by the edible garbage available at open landfills.

Diet: Mostly fish, insects, earthworms, rodents, grain, and garbage. Common fish prey includes alewife, smelt, nine-spined stickleback, and yellow perch; insect meals feature primarily beetles, flies, dragonflies, and bugs. In the western U.S., many Ring-billed Gull populations find most of their food on farm fields, forgoing fish altogether. In addition to their more common fare, Ring-billed Gulls have been known to eat dates, cherries, blueberries, and strawberries, as well as French fries and other food discarded—or left unguarded—by people.

Breeding: Adults are clean gray above, with a white head, body and tail; their black wingtips are spotted with white. They have yellow legs and a yellow bill with a black band around it. Nonbreeding adults have brown-streaked heads. During their first two years, Ring-billed Gulls are a motley brown and gray with a pink bill and legs.

Many, if not most, Ring-billed Gulls return to breed at the colony where they hatched. Once they have bred, they are likely to return to the same breeding spot each year, often nesting within a few meters of the last year's nest site. Many individuals return to the same wintering sites each winter too. Ring-billed gulls nest in colonies numbering from 20 to tens of thousands of pairs. They build their nests on the ground near freshwater, usually on low, sparsely vegetated terrain. They may nest on sandbars, rocky beaches, driftwood, bare rock, concrete, or soil. They often choose sites near or underneath low plants to hide them from aerial predators. Nest sites tend to be used for multiple seasons, by new or returning pairs.

The male and female cooperate in constructing the nest—a scrape in the ground lined with twigs, sticks, grasses, leaves, lichens, or mosses. Some nests are minimalist affairs with almost no lining. The nest's outer diameter ranges from about 10 to 25 inches, with an inner cup about 9 inches in diameter and 2 inches deep. Ring-billed Gull nesting colonies normally include a small percentage of two-female couples. Fertilized by an obliging male, each female spouse lays a clutch of eggs, leading to 5–7-egg "superclutches."

Some Ring-billed Gull nests at study sites in California and Oregon contained pebbles the size and shape of gull eggs. The parents apparently pulled the pebbles into their nests from the surrounding ground, mistaking them for eggs gone astray.

Cool Facts: Migrating Ring-billed Gulls apparently use a built-in compass to navigate. When tested at only two days of age, chicks showed a preference for magnetic bearings that would take them in the appropriate direction for their fall migration. The gulls also rely on landmarks and high-altitude winds to provide directional cues.

Ring-billed Gulls are strong, graceful flyers. They can race along at more than 40 miles per hour, and they're adept at snatching food from the air. You may see these birds hovering, soaring, or poised and stationary in the wind. Adults play by repeatedly dropping objects, then swooping to catch them—perhaps honing their hunting moves. These gulls use a wide variety of foraging methods: walking around on land; stamping their feet in shallow water to uncover small invertebrates; skimming shallow water for small fish; nabbing insects out of the air. They steal food from other birds, hunt for small rodents, and scavenge along beaches, parks, and garbage dumps. Birds in large non-breeding groups usually space themselves evenly, about 3–6 feet apart. Like many other gull species, when Ring-billed Gulls are feeling aggressive they'll lower their head, begin calling, and then raise their head up to their shoulders. This can escalate to an exaggerated toss of the head over the back while calling. To signal submission, a Ring-billed Gull will draw its head back in toward its shoulders and make shorter, calmer calls, sometimes tossing its head up or away from its opponent as well.

Found in Songbird Remix Freebies (Seabirds2)

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