MIGRATION OF ANIMALS. 279 



ern parts of the continent of Europe, and visit and revisit in 

 their migrations the shores of the Mediterranean, Sicily, and 

 the islands of the Archipelago." 



' Beside those birds which retire in the winter from tem- 

 perate to more southern climates, there are many others which 

 spend the summer in the northern regions, and seek a milder 

 residence during the winter in the same countries from which 

 the former have migrated. Thus in every country or district 

 a double migration takes place. There are two sets of birds, 

 one which frequents it in the summer and another in the win- 

 ter. The former are called summer birds of passage, the lat- 

 ter, winter birds of passage. The summer residence of the 

 birds of passage, which frequent temperate climates in the 

 winter, is not always known, but many of them have been 

 traced to northern countries. The snow-buntings, which are 

 common in Great Britain during the winter, retreat in the 

 summer to the polar regions of Spitzbergen, Lapland, and 

 Greenland, where they pair and produce their offspring.' Mar- 

 tin, in his History of the Hebrides, or Western Isles, informs 

 us, that wild swans arrive in great numbers in Lingey, one 

 of the Hebrides, in the month of October, and remain there 

 till March, when they retire more northward to breed. For 

 this purpose, the swans, like most other water-fowls, prefer 

 such places as are least frequented by mankind. During sum- 

 mer, the lakes, marshes, and forests of Lapland are filled with 

 myriads of water-fowls. In that northern region, swans, geese, 

 the duck tribe, goosanders, divers, &,c., pass the summer; 

 but in autumn they return to more hospitable shores. 



The wild goose, which breeds in the most retired regions 

 of the north, arrives in temperate regions at the beginning 

 of winter, and departs early in the spring. Their periodical 

 movements are familiar to all. They fly at a great height, 

 and observe the utmost regularity in all their movements. 

 Many birds of the duck kind are also winter birds of passage 

 They are found in great abundance upon the shores, islands, 

 and rivers of the temperate regions during the cold months ; 

 but, on the approach of summer, migrate to Lapland, Greenland, 

 and Spitzbergen. 



The solan geese, or gannets, are birds of passage, which 

 pass their summer and breed upon the most northern shores 

 and islands of Scotland. The multitudes which frequent 

 these places are prodigious. " There is," says a writer who 

 has given some account of them, " a small island in the Frith 

 of Forth, called the Bass Island, which does not exceed a mile 



