COMMON TERN.
This Tern, known as the Sterna hirundo of Linnæus, by most British ornithologists, although there can be little doubt that the great Swedish naturalist applied the term indiscriminately to this and the Arctic Tern, is one of the best known British species, especially round the English and Welsh coasts. It becomes rarer in Scotland, where it is largely replaced by the Arctic Tern. The Common Tern, distinguished by its white underparts from the Arctic Tern, is migratory and arrives on the British coasts towards the end of April, retiring south in Autumn. Its favourite haunts during the summer are the various groups of low rocky islands, and the more secluded portions of the coast where sandbanks and shingle occur. Save on passage, this Tern is seldom seen far from the vicinity of its nest colony. The flight of the Common Tern is exceedingly buoyant and graceful, the long slender wings and acutely forked tail assisting greatly in the general effect. Like the Swallows the tarsus of the Terns is remarkably short, so that on the ground the birds seem awkward, and rarely attempt to walk far; on the sea, however, they are quite at home and swim well. There are few prettier sights along the shore than a flock of Terns busy in quest of food. Where the beach is rocky, and the water somewhat deep inshore, the birds may be watched with ease. In a serried throng they flutter to and fro; ever and anon a bird falls down like a fragment of white glittering marble into the sea with a loud splash, and in a moment rises again with its finny prey. Bird after bird keeps dropping so; now and then a bird remains swimming on the water; now and then two birds chase each other in rapid flight. And so for miles the Terns will continue to follow the shoal until hunger is satisfied, or the fish retire to greater depths. The food of this species is chiefly composed of small fish, but insects and crustaceans are also devoured. The note of the Common Tern is a shrill krick or kree-ick, most frequently uttered when the bird is flying alarmed over its invaded nesting place.
The Common Tern is rather a late breeder, its eggs not being laid until the end of May or early in June. It breeds in companies of varying size, the suitability of the site being in some measure a determining cause. This Tern is equally capricious in the site selected for the nests; sometimes one spot is chosen, sometimes another; but there can be little doubt that the bird pairs for life, and evinces considerable attachment for its accustomed haunts. I have found almost invariably that the Common Tern habitually lays its eggs farther from the water than the Arctic Tern, and always prefers to conceal them amongst vegetation of some kind. Islands are always preferred to the mainland, doubtless because of their greater safety. We cannot class this bird as an elaborate nest builder, a mere hollow, scantily lined with a little withered grass or weeds, being the only provision. The two or three eggs vary from buff to grayish-brown in ground colour, blotched and spotted with several shades of rich brown and gray. But one brood is reared, and as soon as the young are strong upon the wing, the nesting places are deserted, and the movement south begins.
Terns migrate leisurely in autumn, often remaining a day or so here and there, on and off the coast, and are then seen in localities which they never frequent during summer.