The Great Black-backed Gull is one of the least gregarious of the family, and the large gatherings of this species that are sometimes witnessed are chiefly due to such accidental causes as an unwonted supply of food, or a continued spell of boisterous weather, which often drives Gulls in thousands into sheltered bays and estuaries. This Gull is generally met with beating about in a solitary manner; less frequently three or four may be seen together; whilst even in the breeding season, when most Gulls congregate into colonies whose size seems only to be regulated by the accommodation presented, it is certainly the least sociable of all the British species. It is a great nomad during the non-breeding season, often wandering far from land, resting and sleeping on the sea. On the other hand, it is one of the least frequent visitors of the Gull-tribe to inland districts, and, as its specific name of _marinus_ indicates, is closely attached to the sea. The usual call-note of this fine Gull is a loud, whining, oft-repeated _ag-ag-ag_. Notwithstanding the purity of its plumage, and the magnificence of its presence, the Great Black-backed Gull is almost as unclean in its habits as the Raven or the Vulture. No kind of carrion is refused, either lying on the shore or floating on the sea—weakly, death-stricken lambs or wounded birds, eggs or chicks left unguarded by their owners, fish basking or sleeping near the surface, offal cast from the fishing boats or quays, animal refuse of all kinds, form the prey of this Gull. The usual breeding place of this Gull is the top of an isolated rock stack, a little distance from the mainland; less frequently it selects a range of high cliffs overhanging the sea. A small island in a mountain loch is sometimes selected, and occasionally this may be some considerable distance inland. In a few chosen spots the birds nest in such close, if somewhat scattered proximity, that we might call it a colony, but the rule is for odd and more or less isolated pairs to be met with, and often at considerable distances apart. The fact that this Gull may be found nesting in one chosen spot year by year, warrants the supposition that it may pair for life. The usually scanty nest is made in a hollow amongst the short turf, or heath, or on the flat ledge of a precipice. Sometimes the eggs are laid in a bare hollow amongst the rocks. It is formed of grass, dry sea-weed, twigs, and stalks of marine plants, and occasionally a tuft of wool or a few odd feathers are placed in the lining. The eggs are usually three in number, but sometimes only two, or even one. They are grayish-brown, or brown sometimes tinged with olive in ground colour, spotted with dark umber-brown and brownish-gray. This Gull is a very light sitter, but is bold and clamorous when disturbed from the nest. LESSER BLACK-BACKED GULL.