2i6 BIRD BEHAVIOUR 



and in the New World the Mocking-birds (Mimus) 

 are essentially southern, though the most celebrated 

 (M. 'polyglottus) ranges into the northern states. The 

 only point in which the birds of temperate climates 

 really excel the tropical forms is in power of flight, 

 which they have had perforce to cultivate, and 

 even this superiority is not universal, for there are 

 some of the most magnificent flyers among the 

 Parrots and Pigeons, which are essentially tropical 

 to say nothing of Frigate-birds and Tropic -birds. 



In addition to influences of this kind, which are 

 operative on young and old birds alike, there is the 

 instinctive attachment to the breeding-place, which 

 is so strong in birds that they have often been 

 recorded as returning to it for many years in suc- 

 cession. This of course must act to a certain 

 extent on the old birds, and even the young, if 

 at all uncomfortable where they find themselves 

 by the time they complete their first year, are 

 most likely to come back to the place which gave 

 them birth, and where they had their first insight 

 into the enjoyments of flight and independence. 



The main point about migration, therefore, is 

 the fixing of the methods, not the motive ; and it 

 is here that we are confronted with problems 

 difficult to solve. The case of the Homing Pigeon 

 ought to give us some help, but such Pigeons are 

 well known to be guided almost entirely by sight, 

 and to need training by gradually increased stages ; 

 whereas birds of passage frequently, perhaps most 

 commonly, fly by night, and, in the autumn migra- 



