The terns, of which there are five breeding-species in the British Islands, are all migrants, and come to us in spring. The arctic tern ranges farthest north: it is the most common species on the coasts of Scotland and its islands; its most southern breeding-station is at the Farnes, off the coast of Northumberland. It breeds in communities sometimes numbering thousands of birds. The nests are placed very near each other, often within half a yard, among scanty grass and herbage, or on the shingle and sand of the beach, and sometimes on the bare rock. Two or three eggs are laid, greatly varying in their ground-colour, olive, buff, greyish brown, stone, and other tints being found; and the spots and blotches of blackish brown and grey may be few or many. The young birds are at first covered with a yellowish down with dark brown spots, and are very active. When the nesting-ground is entered the birds rise up, and hover in a dense cloud above the intruder’s head, their united powerful screams producing an extraordinary noise, like that of the sea on a shingled beach when the withdrawing wave drags back the pebbles with shrill and grating sounds. In September and October the arctic tern migrates to warmer regions. Common Tern. Sterna fluviatilis. [Illustration: FIG. 107.--COMMON TERN. ⅐ natural size.] Bill, legs, and feet orange-red; entire plumage as in the arctic tern, except the lower parts, which are more nearly pure white. Length, fourteen and a quarter inches. * * * * * So nearly alike are the arctic and common terns that it is hard, well-nigh impossible, in fact, to distinguish them when they are observed flying about in company. In size, manner of flight, language, and general appearance, they are identical. On a close examination the common tern is found to be slightly less slender in build, its under parts dull white instead of pale grey, its beak tipped with black and coral-red, instead of blood-red. It is doubtless owing to their similarity that the two species associate freely together at all times, and are often to be found breeding side by side. But while the arctic tern is most common in the north, from the Shetlands, Orkneys, and Hebrides, to the coast of Northumberland on the one side of the country, and of Lancashire on the other, the common tern is common only on the coasts south of these two points. The nest is a slight depression, sometimes with a little dry grass for lining, placed on the shingle of the beach; the three eggs are yellowish stone, grey, or olive colour, spotted and blotched with dark brown and grey. Roseate Tern. Sterna dougalli.