in] SPREADING 65 



that the breeding as such is not a prime reason for 

 their wanderings. 



The phenomenon of migration, in its most striking- 

 cases, is now very complicated. Many a bird goes to 

 the very arctic regions for the shortest of summers, 

 and it spends most of the year within the tropics or 

 it may even overshoot the equator and winter in 

 a south temperate country. On the other hand the 

 members of many species do not all go so far north, 

 but stop and breed in the intermediate regions. We 

 must not take the extremes when trying to unravel 

 the development of the problem. 



It has been argued with some show of reason that 

 the real home of a bird is that country in which it 

 was born, where the species breeds, but this is not 

 in every case a valid conclusion. Although it applies 

 to most creatures, there are so many exceptions that 

 we must leave sentiment aside. When it comes to 

 a question of domicile, the ten weeks' sojourn of the 

 swift in England are to be set against the nine months 

 or more which these birds spend in Africa. The 

 breeding time is the busiest period of a bird's life. 

 Then the numbers of each species are suddenly 

 multiplied and so is the stress of providing food, and 

 the particular kind of food which is best for the 

 young may not be available in every country. 



Speaking broadly, any migratory bird breeds in the 

 coldest climate which it visits on its migration ; this 



y. 5 



