WINGED VOYAGERS. 77 



human kinsmen, learn by experience and tutelage, 

 and are also gifted with a sure instinct that amounts 

 in many cases almost to reason. Take, for instance, 

 this one fact. As the sun creeps northward in the 

 spring, it pours a more and more intense heat upon 

 the northern portions of the tropical and sub-tropical 

 regions. The heat would soon become intolerable 

 to certain birds, which have doubtless tried the 

 experiment of spending the summer in equatorial 

 countries ; or if individuals now living have not 

 tried it, perhaps some of their more or less remote 

 ancestors have. That birds do make experiments 

 is proved by the fact that several pets of mine 

 will carefully " sample " a new kind of food offered 

 them, and if they do not find it to their taste, 

 will let it severely alone ; nor is it any the less 

 evident that young birds receive instruction from 

 their elders. Thus the necessity of leaving the 

 torrid regions as summer approaches may have 

 been impressed on the migrating species from time 

 immemorial. 



Again, as spring advances, insect and vegetable 

 life is revived in regions farther north, and this 

 certainly must act as a magnet upon the birds, 

 drawing them from point to point as the supply of 

 food becomes scarce in the more southern localities. 

 Then, let us suppose for a moment that all the birds 

 did remain in the south through the summer ; there 

 would sooner or later be a bird famine in the land, 

 for the supply of seeds and insects would soon be 

 exhausted. Our feathered folk are simply obliged, 



