178 The Migration of Birds 



thing for us to think about. This question concerning 

 the cause of migration is often answered to the satis- 

 faction of many by the statement that "The old birds 

 lead the way, and the young follow." If this is a 

 logical answer, how are the believers of this theory 

 to account for the fact that sometimes the young of 

 certain species go first; also how would they account 

 for the restlessness during the migration season of 

 caged birds that were taken from the nest before they 

 could fly ? 



The Origin of Migration. Why do birds 

 migrate ? This is a fascinating subject and one much 

 indulged in by bird students, probably for reasons 

 known to themselves, but apparently because each has 

 a pet theory that the others cannot disprove. General 

 statements concerning migration may stand approved, 

 but when we consider the details of the subject, it 

 is easy to ask questions which it is impossible to 

 answer. Whatever theories may be advanced in ex- 

 planation of migration, it should be remembered that 

 birds are very conservative and habits once formed 

 may be maintained for ages, though they ceased long 

 ago to be useful. Therefore in considering the origin 

 of migration we cannot expect to find it wholly in the 

 present condition, but we must at least go back to 

 a time before the Glacial period. 



