MIGRATION 1 7 



from Greece to Iceland. What is left of Arabia and Africa, after 

 taking off the above portions, with the addition of Madagascar 

 and the Mascarene Islands, is the Mhiopian Eegion ; and all the 

 rest of continental Asia, with the islands not included in the 

 Australian Eegion, becomes the Indian, or, as it has lately been 

 called, the Oriental. It would be quite impossible to enumerate 

 here the various Sub-regions and Provinces into which these 

 several Eegions may be divided. The views of Mr. Wallace are 

 set forth at length in his excellent work, those of Mr. Sclater in 

 The Ibis for 1891, pp. 514-557, ^nd those of Professor Newton 

 in his Dictionary of Birds. Many writers would assign to Mada- 

 gascar a higher rank than that of a Sub-region. 



Migration. — Few peculiarities of Birds have excited more 

 general interest than their seasonal Migration, which in many 

 species is so marked as to have been observed from very remote 

 times ; and it is probable that nearly all species are subject to 

 periodical movements of varying extent. These movements are 

 greatest in the Birds which have their breeding quarters iu the 

 northern parts of the Northern Hemisphere ; and, with some 

 exceptions, it may be said that the more northerly is the range 

 of a species the more extensive are its migratory wanderings. 

 In the Southern Hemisphere the facts known are as yet 

 insufficient to allow of safe deductions. Absence of a food- 

 supply in winter is alone enough to account for migration in the 

 above cases, and the return from the south in spring is prob- 

 ably due to the desire of Birds to reoccupy their old haunts, or 

 those in which they have been bred. But just as there are some 

 species which habitually breed within the Arctic Circle and winter 

 in the Tropics, there are others which may not go so far in either 

 direction, and yet have their movements governed by exactly the 

 same principle, with the result that in a temperate zone we 

 have Birds coming from the north to winter with us, while 

 others, arriving from the south in spring, spend the summer 

 here, and depart towards autumn. Others again, the true " Birds 

 of Passage," arriving like the last in spring, make little or no 

 stay, but pass onward to more northerly lands, and re-appear for 

 as short a time in autumn on their return journey southwards. 

 Moreover, observation shews that, in most parts of the temperate 

 zone, there are many Birds which, though resident as species, are 

 migratory as individuals — -that is to say, that while examples of 

 VOL. IX c 



