I. GEOGEAPHICAL DISTRIBUTION OF BIRDS. 



GENERAL LAWS OF GEOGRAPHICAL DISTRIBUTION.* 



The true home of a bird is the locality where it breeds ; where the 

 food and surroundings are best suited for its existence, and where it 

 would probably remain permanently were it not for the changes due 

 to the approach of winter, which drive it southward to a more con- 

 genial clime until the return of spring makes its home once more 

 habitable. 



In the wide extent of country through which a bird passes during 

 its migrations, it is but a transient visitor, and is obviously not to be 

 considered as one of the species native to that section. 



It is evident then that all study of the distribution of bird life, and 

 the laws which govern it, must be made during the breeding season, 

 when all birds may be considered at home. 



The distribution of birds, it should be remembered, is subject to 

 the same general laws that govern the distribution of other animals, 

 as well as plants. That is to say, where the conditions of climate 

 and environment are suitable to the existence of certain species of 

 birds, there we shall find certain species of mammals and plants ; 

 and where the character of bird life is decidedly different, there we 

 may confidently expect a different flora. It can thus be easily seen 

 how intimately related are the studies of the distribution of animals 

 and plants, and how much aid they are likely to prove to one another. 

 The distribution of life is dependent either directly or indirectly upon 

 climate, the differences in the tropical, temperate and polar faunas 



* The following papers should be consulted for a full discussion of this ques- 

 tion : 



J. A. Allen, " On the Mammals and Water Birds of East Florida * * * 

 And a Sketch of the Bird-Faun« of Eastern North America." — Bull. Mus. 

 Comp. Zool., II., p. 161. 



Dr. C. Hart Merriam, " Results of a Biological Survey of the San Francisco 

 Mountain Region and Desert of the Little Colorado, Arizona" (Parti.). — North 

 Amer. Fauna, No. 3. 



J. A. Allen, " Origin and Distribution of North American Birds." — The 

 Auk, 1893, p. 97. 



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