Ring-billed Gull (Larus delawarensis)
Ring-billed gulls switch mates from year to year but because this bird is very faithful to its nesting site, returning to the same area each year, the mates chosen are often previous nest neighbours.
The ring-billed gull is a relatively large gull, measuring 48 cm in length- about the size of a crow. Its body, head and tail are white and its back and wings are pale grey, with black tips. This gull is difficult to distinguish from several similar gulls, but can be identified by its size, yellow legs and eyes, and the black ring near the tip of its yellow bill. It is smaller than a herring gull, appearing more buoyant and manoeuverable in flight. Immature gulls are mostly brown and grey, with black wingtips, pink-grey legs, a white rump and a white tail with a black band near the end.
The ring-billed gull breeds locally throughout the southern parts of Canada, from the Atlantic coast west to central Alberta. In the Atlantic region, it breeds in Newfoundland, Prince Edward Island, parts of Labrador, and along the shores of the St. Lawrence River, although it is not particularly common in any of these areas. It winters along the Atlantic coast from the Maritimes south to Mexico, in the Great Lakes, and along the Pacific coast of the United States and Mexico.
This gull occurs in freshwater as well as marine environments. It inhabits lakes, rivers, islands and coastlines, and also forages in garbage dumps and farmersí fields. Invertebrates, fish, small mammals, birdsí eggs and garbage make up its diet, and feeding is accomplished by picking insects and grubs from the ground, diving from the air to catch organisms swimming near the surface, and dipping its bill underwater to pick up food particles.
The ring-billed gull nests in colonies, often associating with other species of gulls. The saucer-shaped nest is woven of grass, twigs and other debris in a scrape on the ground, sometimes hidden among rocks. The female lays 2-4 buffy, spotted eggs, which are incubated by both parents for about 21 days. Most pairs are monogamous, although sometimes males mate with several females, or two females may form a pair on their own - a combination which does not result in offspring.