248 THE BOOK OF MIGRATORY BIRDS 



instead of frustrating, really eases and raises them in their 

 flight. 



The late famous M. Brehm puts it thusT "Every bird 

 has its native country, where it freely reproduces, and 

 remains part of the year, travelling in the remainder. 

 Most birds spend half of the time at their home, and pass 

 the other half in travelling. Some, particularly birds of 

 prey, travel by day; but by far the greater part go by 

 night; and some perform their migrations indifferently 

 either by day or night. They seem to pass the whole of 

 their migration without sleep, for they employ the day in 

 seeking for food, stopping in the places where they are 

 most likely to find it. They commonly keep very high in 

 the air, and always at nearly the same distance from the 

 earth, so that they rise very high over mountains, and fly 

 lower along valleys. 



