Ireland's long and varied coastline and location on the edge of the North Atlantic unsurprisingly makes it suitable for many seabirds. Breeding gulls are joined in winters by many migrants, in some years there may be any Iceland and Glaucous Gulls and occasional rarities. Terns are generally summer visitors with large colonies in County Wexford and Rockabill Island in the Irish Sea, with smaller colonies elsewhere. The Roseate Tern population is of particular importance in a European sense. Some tern colonies have declined greatly in recent years which is of concern. Most Skuas are passage birds moving to and from nesting grounds further north, though one or two pairs of Great Skua now nest each year.