OCR Text |
Show 22 ISLAND LIFE. [PART I. sub-species. It seems to be found in all the southern mountains of China, from Foochow on the east to Sze-chuen and East Thibet on the west, as it is recorded from Moupin by the Abbe David as well as the Himalayan bird--a tolerable proof that it is a distinct form. 10. Garruhts taivanus.-The Formosan jay is a very close ally of the preceding, confined to the island of Formosa. 11. Gan·1d~ts japonicus.-The Japanese jay is very closely allied to our common British species, being somewhat smaller and less brightly coloured, and with black orbits; yet these arc the most widely separated species of the genus. 12. Garrulus lidthi.-Tbis is the handsomest of all the jays, the head, neck, and wings being azure blue. Its locality was long doubtful, but it has now been ascertained to inhabit Japan, where it is evidently very rare, its exact habitat being still unknown. · In the accompanying ma.p (see frontispiece) we have laid down the distribution of each species so far as it can be ascertained from the works of Sharpe and Dresser for Europe, J erdon for India, Swinhoe for China, and Messrs. Blakiston and Pryer for Japan. There is, however, much uncertainty in many places, and gaps have to be filled up conjecturally, while such a largo part of Asia is still very imperfectly explored, that considerable modifications may have to be made when the country becomes more accurately known. But though details may be modified we can hardly suppose that the great features of the several specific areas, or their relations to each other, will be much affected; and these ~re what we have· chiefly to consider as bearing on the questions here discussed. The first thing that strikes us on looking at the map, is, tbe small amount of overlapping of the several areas, and the isolation of many of the species; while the next most st.riking feature is the manner in which the Asiatic species almost surround a vast area in which no jays are found. The only species with large areas, are the European G. glandari·us and the Asiatic G. Brandti. The former has three species overlapping it- in Algeria, in South-eastern and in North-eastern Europo respectively. The Syrian jay (No. 4), is not known to occur anywhere CHAr. II.] THE ELEMENTARY FACTS OF DISTRIBUTION. 23 with the black-headed jay (No. 3), and perhaps the two areas do not meet. The Persian jay (No. 5), is quite isolated. The Himalaya~ and Chinese jays (Nos. 7, 8, and 9) form a group which ~re Isolated ~rom the rest of the genus ; w bile the Japanese .~ay (No. 1~), IS also c?m.pletely isolated as regards the European J~ys _to ';hwh alone It IS. closely allied. These peculiarities of d1stnbut10n are no doubt m part dependent on the habits of the jays, which live only in well-wooded districts, among deciduous trees, and are essentially non-migratory in their habits, thou<Yh sometimes moving southwards in winter. This will explain their absence from the vast desert area of Central Asia, but it will not account for the gap between the North and South Chinese species, nor for the absence of jays from the wooded hills of Turkestan, where Mr. N. A. Severtzoff collected assiduously, obtaining 384 species of birds but no jay. These peculiarities, and the fact that jays are never very abundant anywhere, seem to indicate that the genus is now a decaying one, and that it has at no very distant epoch occupied a larger and more continuous area, such as that of the genus Parus at the present day. Discontinuo~ts generic Areas.-lt is not very easy to find good examples of genera whose species occupy two or more quite disconnected areas, for though such cases may not be rare, we are seldom in a position to mark out the limits of the several species with sufficient accuracy. The best and most remarkable case among European birds is that of the blue magpies, forming the genus Cyanopica. One species (0. cooki) is confined (as already stated) to the wooded and mountainous districts of Spain and Portugal, while the only other species of the genus (0. cyanus) is found far away in North-eastern Asia and Japan, so that tbe two species are separated by about 5,000 miles of continuous land. Another case is that of the curious little water-moles forming the genus Mygale, one species M. muscoviticct, being found only on the banks of the Volga and Don in South-eastern Russia, while the other, ..1..lf. pyrenaica, is confined t.o streams on the northern side of the Pyrenees. In tropical America there are four different kinds of bell-birds belon<Yin<Y to the genus b b Chasmorhynchus, each of which appears to inhabit a restricted |