160 MIGRATION A MYSTERY 



reproduction were over, and the young safely reared 

 and able to fend for themselves; when clouds and 

 showers had mitigated the excessive heats and dry- 

 ness of midsummer, and the weather was most genial 

 and all bird food fruit, seed and insects most 

 abundant; and finally when they had come into the 

 serenest and sweetest time of their lives, with nothing 

 to do but rejoice in the sunshine, feast and grow 

 fatter and tamer every day, and, one would imagine, 

 when they would be least inclined to set out on 

 a weary and perilous journey of hundreds and 

 thousands of miles. 



It is not only in southern South America that 

 birds quit their homes just when the life conditions 

 are most favourable; it is the rule in all temperate 

 regions, although it may not seem so in these brumous 

 northern islands. 



However, the easy explanation that birds went 

 away because they would do better elsewhere, 

 although it is still put forward in Newton's Dictionary 

 of Birds and the Encyclopedia Britannica, was never 

 regarded as a quite sufficient cause. How did the 

 bird know the young bird, let us say, that migrates 

 alone that he would do better elsewhere? After 

 all, then, migration was a mystery; so much a 

 mystery that the greatest man of science this country 

 has produced, who discovered the laws that govern 

 the motions of the heavenly bodies, said of the migra- 

 tion of birds that it was directly inspired by the 

 Creator, since no other explanation was possible. 



If I remember rightly something I read as a boy, 



