Habitat

Predominantly islands (in broadest sense of word), including major offshore islands, rocky islets, dredge tailings, marshy hummocks, barrier beaches. Adults prefer dry, well-drained substrate, e.g., rock or sand, but highest breeding success often achieved in vegetated areas with adequate cover (from both weather and predation) for semiprecocial young (Pierotti 1982, 1987a). Nests in greatest densities on rocky marine terraces in Witless Bay, Newfoundland (Pierotti 1982; also see Fig. 2). Several hundred pairs also nest in cities (e.g., Boston, MA; Portland, ME; Halifax, Nova Scotia; St. John, New Brunswick) on rooftops near water (RJP).

Major requirements appear to be area free of and inaccessible to terrestrial predators and nest sites sheltered from prevailing wind (Pierotti 1982). Typically nests in association with numerous conspecifics. Coloniality appears facultative, since many Herring Gulls nest solitarily on offshore rocks, rooftops, and rocky islets in inland lakes (RJP).

Foraging habitat typically spatially separate from nesting habitat. Forages at sea, in intertidal, on sandy beaches and mudflats, in refuse dumps and ploughed fields, and around picnic areas or fish-processing plants. A few birds forage on breeding colonies by taking eggs and young of conspecifics and other seabirds (Pierotti and Annett 1987, 1991).

Uses open areas as roosting sites, including parking lots, fields, helipads, airport runways.

See Migration. Marked differences exist between populations; birds from Nova Scotia and Cape Ann and Boston, MA, remain around breeding colonies throughout year, whereas birds from Maine, Gulf of St. Lawrence, and Newfoundland disperse southward (Drury and Nisbet 1972, RJP, TPG). Outside breeding season, nearly all individuals associated with foraging habitats, especially during daylight, and roost in areas adjacent to foraging sites.