VI. 



The Migration of Birds. 



''pHE subject of the Migration of Birds is one which has attracted 

 J- much attention in times both ancient and modern. It is only, 

 however, during recent years that any light has been thrown on the 

 probable origin of these periodical movements by the collection of 

 new facts and observations from every part of the world, so that now 

 the general principles and laws which govern the movement are 

 capable of being better understood, and the chosen paths of the 

 bird through the air remain no longer shrouded altogether in 

 mysterious gloom. 



In the new volume, mentioned below, Mr, Dixon has brought 

 together from various sources, doubtless with much painstaking 

 research, a great array of facts bearing on this special subject, and 

 these he has endeavoured, how far successfully we must judge, to 

 reduce to some system or law. 



The book is divided into twelve chapters, with special headings, 

 and the first of these deals with ancient and modern views of migra- 

 tion and the presumptive habit of Hibernation ; in the terrestrial 

 form of which, as opposed to the subaqueous, Mr. Dixon seems to 

 retain some sort of belief, and as a suggestive fact, which he thinks 

 deserves notice, tells us that the winter quarters of the two most 

 northerly ranging of the Hirundinidae, namely, the house and the sand 

 martin, are yet practically unknown. Is it possible, he asks — without 

 venturing to express any decided opinion — that the most northerly birds 

 hibernate and pass the long boreal winter in torpidity ? Mr. Dixon 

 does not seem to be aware that both these species, which have a most 

 extended range, cross the Mediterranean, in spring and autumn, on 

 migration in great number, and the range of the latter is known to 

 go as far south as the Transvaal. 



The subject of the hibernation of some birds may, however, be 

 dismissed as unworthy of serious consideration. 



Passing to the subject of Migration, the author thinks that birds 

 change their countries from necessity, and that instinct or hereditary 

 desire gives the impulse to move, but then gives place to reason, 

 memory and knowledge of locality. He is evidently no believer in the 



' The Migration of Birds. An attempt to reduce Avian Season-flight to 

 Law. By Charles Dixon. London : Chapman and Hall, 1S92. 



