THE MIGRATION OF BIRDS 



merely to the same county or parish, but to the same 

 farmyard. The same return to the original home- 

 stead has been proved in the case of the house- 

 martin and the stork, and is certainly one of the 

 most wonderful facts about migration. 



Difficult Questions 



Comparatively little is yet known in regard to the 

 paths that birds follow in their migratory flight. 

 From the shores of the Baltic the storks migrate in 

 autumn southwards and south-eastwards to South 

 Africa. Many swallows seem to fly more or less 

 directly from north to south. Many birds, such as 

 hooded crows, show in autumn a great westward 

 movement along the shores of the Baltic, with a 

 subsequent curve towards the south. Some con- 

 tingents swerve southwards by the valleys of the 

 Rhine and the Rhone, and then across the Mediter- 

 ranean to North Africa. Other contingents seem 

 to go farther westwards, crossing, it may be, by way 

 of Heligoland to the South of England, and thence 

 across to France, Spain and Portugal, finally 

 landing like the others in North Africa. These are 

 but a few examples of known routes. 



Other matters for investigation, which must be 

 patiently continued without hurrying towards an 

 answer, are the altitude and the velocity of the 

 migratory flight, and its relation to weather con- 

 ditions. While enormous armies of larks, starlings, 

 thrushes, and some other birds have been seen flying 

 very low across the sea, it is probable that most 

 migrants fly at a considerable height. Careful 



149 



