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Show 1876.] MR. H. SAUNDERS ON THE STERCORARIlNA. 329 whilst the offspring of two similar parents will "breed true." This point can only be solved by some ornithologist who will devote his attention to a colony during the breeding-season, observing tbe produce of all these unions, and, if possible, marking the nestlings before they take wing; perhaps some of our Scotch friends will take the hint. That the sooty plumage is not merely a sign of immaturity is shown by the long tail-feathers, and by the burnished tinge of the acuminate ones on the nape. It is worthy of notice that in Spitzbergen, its most northern breeding-ground, neither Dr. Malmgren nor Professor Newton found a single example of the dark whole-coloured form ; all those which Admiral Collinson's and Dr. Rae's Expeditions brought home from the far north are also white-breasted specimens, which looks as if the dark form was a more exclusively southern one. In the white-breasted birds the striations on the underparts decrease with age until little more than a pectoral band remains ; this, again, becomes narrower until in some specimens it entirely disappears and the bird is white from the chin to the abdomen. This species has the most extended range of any member of the family. Parry found it up to lat. 82° 2' N.; and it breeds throughout the arctic and subarctic regions, as far south as the islands of the north of Scotland ; and Thompson records it as having nested near Achil Island on the west of Ireland. I should not be surprised to learn that there is some beeeding-place along the western shores of France; for both old and also very young birds occur at Malaga early in August. Some go higher up the Mediterranean ; but others, principally the young, continue their course along the west coast of Africa, to Walwich Bay and as far as the Cape of Good Hope; and in those waters they pass the months of what is our winter, compelling the Terns and the small Gull (L. hartlaubii) to disgorge their prey. From the altered appearance which they present in their progressive stages of plumage at a time when European naturalists have lost sight of them, an individual from the vicinity of St. Helena received the name of S. spinicauda. Careful examination of a series of specimens from the Cape of Good Hope, where Mr. E. L. Layard only observed them from December to February, showed that all were in the act of losing and renewing the central tail-feathers and the outer primaries, which are the last to be moulted ; and although at the first glance the birds have a somewhat distinct look, yet there can be no doubt whatever of their being our northern species. Most that I have seen are birds of less than a year old, although this immaturity is less noticeable in the dark-plumaged birds than in the lighter ones; in none, however, are the central tail-feathers fully developed, and most are still partially in the quill-sheath. One specimen, evidently obtained just before the northward migration, is absolutely the same as a bird of only two months older from the Faroes. It is to be presumed that S. crepidatus goes up the east coast of Africa, as M r . Allan H u m e obtained it (naming it A asiaticus), and observed many along the coast of Sindh, the Gulf of Oman, and between Guader and Bombay. |