i64 THE BIOLOGY OF BIRDS 



crossing, it may be, by way of Helgoland to the South of 

 England, and thence across to France, Spain, and Portugal, 

 finally landing like the others in North Africa. For some 

 other birds, like the swallow and the Red-Spotted Blue- 

 throat, there is considerable evidence of a more direct north 

 to south movement in autumn. Large numbers of swallows 

 are seen in autumn making their way down the west coast 

 of Africa, perhaps reaching the Cape ; those from Eastern 

 Europe are said to work their way southwards by the Nile 

 Valley. Corresponding species or varieties of swallow in 

 North America seem to fly southwards to Brazil, and in 

 North Asia to Burma " (Thomson, " The Wonder of Life," 

 1914, p. 172). 



For European birds, Lucanus distinguishes three routes 

 that have been satisfactorily demonstrated. Firsts there is 

 the west coast route, which extends from east to west along 

 the southern shores of the Baltic, along the coasts of France 

 (and the southern coast of England), southwards to Spain, 

 and across to Africa. Among the birds following this 

 path may be mentioned — gulls, terns, snipe, oyster-catchers, 

 lapwings, hooded crows, starlings. 



Second, there is an Adriatic-Tunisian route. Birds gather 

 in eastern and central Europe, and follow both coasts of 

 the Adriatic to the southern end of Italy, whence they 

 cross, via Sicily, to Tunis. This path is followed by 

 some snipe-like birds and by many songsters. 



Third, there is the Italian- Spanish route. Birds gathering 

 in Hungary, Austria, and Southern Germany pass to the 

 south of the Alps across the north of Italy, e.g. along the 

 basin of the Po. Thence some may follow the coast of 

 France and Spain to Gibraltar, while others cross by 

 Corsica and Sardinia, or via the Balearic Islands. This 

 route is followed by thrushes, starlings, plover, and many 

 other birds. 



{h) Height in the Air. — Another question requiring 

 further investigation is as to the height at which birds fly 

 in their migration. Some birds, e.g. larks, starlings, and 

 thrushes, have been seen flying low in enormous clouds 



