256 Habit and histmct. 



matters stand, however, the question must be left open. 

 Like many other cases of instinct, this affords no decisive 

 evidence, and must be relegated to a suspense account. 



We may now pass on to consider, or rather to touch 

 upon, what is the most difficult and perplexing of all the 

 problems which are suggested by bird-life — the migratory 

 habit — of which Professor Newton says that it is "perhaps 

 the greatest mystery which the whole animal kingdom 

 presents." * 



What can one say that is the least fresh and helpful 

 concerning migration ? Little enough. I shall therefore 

 merely give a brief reminder of the facts, an indication of 

 the essential problems from our own special standpoint, 

 some allusion to the theories which have been suggested, 

 and a confession of ignorance. 



The leading facts are sufficiently familiar. A number 

 of om- English birds, like the swallow, the cuckoo, and the 

 nightingale, after nesting with us in the summer, depart 

 southwards in the autumn, and return in the ensuing 

 spring. Others, like the redwing and the fieldfare, come to 

 us in the autumn and depart northwards in the spring to 

 nest and rear their young. Yet others, birds of passage 

 like the sanderling and phalarope, make England merely a 

 resting-place on their southward or northward journey. 

 Even the birds that are with us the year through, like the 

 redbreast and song thrush, receive accessions or suffer 

 diminution of numbers through migration. In the northern 

 hemisphere, whenever, as is commonly the case, the 

 alternate migrations are northward and southward, the 

 nesting-place is in the northern part of the area over which 

 the bird migrates. The distances traversed are great. 

 " The sanderling nests in Iceland or on the shores of the 

 Arctic Ocean, and in winter it has been seen as far south 

 * "Dictionary of Birds," p. 549. 



