276 FIELD ZOOLOGY. 



great movements, not understood except as to their 

 results in peopling lands now widely separated by oceans. 

 The Crusades and the assembling of the Pilgrim fathers 

 upon our own shores, offer two great illustrations of this 

 tendency of the human family to migrate. In the whole 

 range of the animal kingdom the individual must have 

 the inner feeling of satisfaction with his surroundings, 

 or there will crowd upon him the irresistible impulse to 

 find satisfactory surroundings elsewhere. With the 

 human family, this feeling may arise through reasoning 

 out the non-beneficial results of a particular condition; 

 with the animals below man, the impulse to migration 

 must be less a matter of mentation, and predominantly 

 a matter of physical, bodily, discontent. Still, with the 

 highest of the lower animals, there must enter the first 

 stirrings of the impulses that are mental in the animals a 

 little farther up in the scale of life. 



The sexual instinct must play a large part in the 

 migrations of birds. This instinct may be regarded as 

 the expression of the desire of the individual to live on. 

 Failing this possibility within himself, then to live in his 

 offspring; and from this latter feeling may arise the 

 desire to place the offspring in the most desirable con- 

 ditions possible, at whatever cost to himself. 



Birds staying in one region the year round must, 

 if it is in our latitude, temperate, change their fare with 

 the season. But birds that are dependent upon one 

 kind of food, as fruit, must migrate to find it. Insect- 

 eaters must also migrate to follow up the insect hordes. 

 Most migratory birds of the western States pass the 

 winter in Mexico and Cuba. The same general statement 

 may be made for the birds of the eastern United States, 

 most of them go south for the winter. Many of the 



