SOME QUESTIONS CONCERNING MIGRATION 83 



veteran of eighty-eight Dr. Alfred Russel Wallace has 

 severely criticised the view that the young birds make the 

 autumnal journey alone. He admits Gatke's observation, 

 with which the Heligolanders used to be practically familiar, 

 that the young birds arrive first and alone, the adult birds 

 appearing a week or two later. But he rejects the inference 

 that the young birds start on their migration alone, and 

 before their parents. According to Wallace, what probably 

 happens is this : that the older birds and stronger young 

 ones, flying together, pass over Heligoland without stopping ; 

 that those young birds that sink down on Heligoland are 

 the weaker individuals, much fatigued ; and that those 

 adults that arrive later on the island do not represent by 

 any means the main contingent, but rather the crippled, 

 the unmated, the partially moulted, and so on. On this 

 view, he thinks, " all the facts are explained without having 

 recourse to the wildly improbable hypothesis of flocks 

 of immature birds migrating over land areas and sea 

 quite alone, and a week in advance of their parents or 

 guides." 



This criticism is a useful one, and certainly the marvel 

 of migration is great enough without being gratuitously 

 enhanced. On the other hand, practised ornithologists 

 develop observational power to a very remarkable degree, 

 and there are numerous testimonies to the fact that great 

 crowds of young birds have been seen leaving British shores 

 before the adults have got on the move, and that great crowds 

 of young birds have been seen arriving on our shores from 

 the Continent in Autumn with, as far as could be detected, 

 no adults amongst them. It is, indeed, practically impossible 

 to be sure that there are no old experienced hands among 

 the youngsters, but of their apparent absence there is 

 considerable expert evidence. Moreover, it should be 

 pointed out that, even on Dr. Wallace's interpretation of 



