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 THE COMMON TERN.

The (Sterna hirundo, Coloured Plate XXXVIII.), when in its adult plumage, closely resembles the Caspian Sea Swallow, but may be recognised by its inferior size, the grey colour of the under parts of the body, and by its red feet. In young birds the plumage of the back, like that of the preceding species, is transversely spotted with brown, but the feet are of a yellowish shade. The length of this species is from sixteen to seventeen inches; of these six and a half belong to the tail, the fork being four inches deep; the span of the wings is twenty-three inches. It is at present uncertain whether all River Terns are to be regarded as belonging to this species or not. Should they be found to do so, their habitat must extend throughout the whole north temperate zone, seeing that they are pretty equally distributed in the eastern and western hemispheres. They are met with more frequently than other Terns in the vicinity of rivers and lakes of fresh water. As these birds make regular migrations, they are only seen at their breeding-places in the summer, appearing during the last days of April or the beginning of May, and in July or August preparing for their departure. They spend the winter in the south of Europe, or in the north of Africa, where at that season they are very common. When on their journeyings they fly leisurely, and at a considerable elevation, from one sheet of water to another, generally following the course of streams and rivers, to which, if pressed by hunger, they repair, in order to obtain food and rest. Arrived at their destination, they settle themselves either in the vicinity of the sea, or near fresh water, without seeming to have any decided preference for either.

The Common Terns arrive in the south of Europe early in May, and progressing northwards, colonising as they go, visit Ireland, Scotland, and some of the adjacent islands. On inland waters the Terns do not congregate in great numbers. On the sea-shore, on the contrary, as the breeding season approaches, hundreds of them collect together and form large settlements. One of these settlements, on the coast of one of the Canary Islands, was visited by Bolle, who gives the following account of what he saw:—"The farther we advanced the more numerous became the flights of such pairs as we had disturbed, until at length we were obliged to proceed carefully to avoid treading on their eggs, so numerously did they lay around us on every side. Scarcely had we begun to collect some of the eggs in our hats and baskets, than up rose the whole multitude of breeding birds into the air, thousands in number, and overshadowed us like a great white cloud. Their shrieks were positively deafening, and the uproar was still further increased by the appearance of some other men at a little distance, who were likewise collecting eggs. From out of the living screen above us, many of these birds seemed to rush right down upon our heads, and these were probably those whose nests lay nearest to the place where we stood, and were consequently in the greatest danger of being plundered. After a little while, we retired to a distance, whence we could plainly see the different pairs, as they returned to their eggs, upon which the females immediately planted themselves, while their faithful spouses took their stations beside them. We did not leave them, however, till we had completely filled all our baskets with eggs, and this we accomplished in less than an hour. The men above alluded to, informed us that for a few weeks in the year, the place was constantly resorted to by the inhabitants, who eagerly collected the eggs, and that, nevertheless, the number of birds did not seem to diminish; the truth of this last assertion was indeed sufficiently evident." It not unfrequently happens that by some sudden flood in the rivers, or heavy storm at sea, the breeding-places of these Terns are completely inundated, and their eggs consequently destroyed. Should such an event occur early in the season, the parent birds will produce a second brood, but if it happens at a later period, their hope of progeny is at an end. Upon one occasion Naumann had an opportunity of witnessing a fair chase between the Common Tern and the agile Tree Falcon. The Tern did not