Auk 



^22 Taverner, The Origin of Migration. \jy^ 



mately related to the Tyranninae, while morphologically it is 

 intermediate between the latter and the Elaineinse. 



(4) The Tyranninee form a natural section with which perhaps 

 the Pitanginae should be united. 



S. Paulo, Brazil, g IVov., ^903- 



A DISCUSSION OF THE ORIGIN OF MIGRATION. 



BY P. A. TAVERNER. 



One of the first, if not the very first, phenomena of animate 

 nature to be noticed by primeval man, must have been that of 

 migration ; and from that day to this it has been, to a greater or 

 less extent, a subject of great interest to students.* In the present 

 day it has been approached from many different sides, and 

 though many points have been pretty well cleared up, others are 

 still enveloped in a haze through which the fundamental princi- 

 ples are but barely visible, while others still remain shrouded in 

 a dense, impenetrable cloud of mystery. 



The methods by which birds find their way to far distant points, 

 the manner of their migrations, etc., lie without the scope of this 

 paper, and will not be referred to here. Upon these points we 

 all await the publication of the results of the investigations now in 

 progress, when probably many obscure points will be cleared up. 



Migration consists of two movements, one in the spring, away 

 from the winter station ; and the other in the fall, towards it again. 

 The reason of the latter is self-evident. There is a lack of food. 

 If they did not return in the fall they would perish of hunger, if 

 not of cold. From general observations, it seems as if the former 

 had a larger influence than the latter, and it is the northward 

 movement that needs explanation. Why should a bird leave a 

 warm land of plenty to journey to a country but half recovered 

 from the frozen embraces of an arctic climate ? It seems 



