Courtesy Kenn Kaufman
Two subspecies of the Iceland Gull are currently recognized: Kumlien's Gull (L. g. kumlieni) and the Iceland Gull of Greenland (L. g. gloucoides). Kumlien's Iceland Gull breeds from the eastern part of Canada's Baffin Island southward to Southampton Island. This subspecies winters coastally from the Atlantic Provinces south to Virginia and rarely through the Great Lakes. The southern coasts of Greenland host the other subspecies, which winters across a broad range, including the Canadian Atlantic Provinces, Iceland and northwestern Europe. Most Iceland Gulls winter on open waters, called polynyas, set in the Arctic ice.
In winter, the Iceland Gull concentrates at the Arctic sea ice openings created by ocean currents and warm upwellings. Some Iceland Gulls winter in coastal waters and fresh water rivers, lakes, and reservoirs. Steep, rocky cliffs overlooking ice or cold waters are preferred breeding sites.
A visual hunter, the Iceland Gull forages mostly at the water's surface, over slushy ice, or on beaches. They appear less often at garbage dumps than other gulls. In winter, these gulls consume a variety of foods, including fish, eels, clams, snails, fly larvae and adults, and marine worms. Iceland Gulls sometimes prey upon the eggs and chicks of other seabirds, like the Thick-billed Murre and the Black-legged Kittiwake. In summer, this northern seabird times its breeding cycle with the melting of the sea ice, and forages where ice and water meet.
Iceland Gulls assemble at their breeding grounds in late May and early June, in colonies numbering anywhere from 50 to 2,000 pairs. They seem to form monogamous pairs for the season. The nests are built on rocky ledges ranging from near sea level to as high as 400 feet above, using a variety of materials, including grass, moss, old feathers, and turf. For about 25 days, both sexes incubate two to three yellowish to greenish eggs, marked with brown blotches. The downy chicks peck at the adults' bills to receive regurgitated clumps of partially digested food. Juvenile Iceland Gulls fledge in about six weeks and often wander alone, away from the wintering areas used by adults.
In late summer and early fall, most Iceland Gulls appear to travel short distances from their breeding grounds to open waters and ice floes in the north Atlantic, but young gulls move farther south to open coastlines. Some populations may be nomadic in winter. Most Iceland Gulls migrate in flocks and arrive on the breeding grounds between late May and mid-June.