146 BIRDS OF MAINE. 



FAUNAL AREAS. 



Zoogeography, or the geographical distributiou of species, is a 

 comparatively new science, but, nevertheless, one destined to prove 

 of the utmost economic importance to the agriculturist. Plants and 

 animals are naturally found in certain climates where the condi- 

 tions of temperature and surroundings are congenial to them. 

 Some species have the power of adapting themselves to circum- 

 stances and are found in many diverse climates, while others are 

 exclusively confined to certain regions over which the same condi- 

 tions prevail, and need not be looked for elsewhere. These latter 

 are said to be indigenous to a life area, and by aid of these species 

 we are enabled to divide the country into an ultimate number of 

 life areas which are termed fauna?. AVhen by study and observa- 

 tion of a certain plant or animal in various localities, we have 

 finally arrived at the conclusion that wherever we have found that 

 particular species the conditions of climate, surroundings, etc., are 

 uniform, we may then safely say, on hearing from some outside 

 observer that this same species is found in his locality, just what 

 the climate and surroundings of that locality are, without ever hav- 

 ing seen it. Of course we are always open to error due to the fact 

 that this species may be able to adapt itself to other conditions, 

 but from a close and long-continued study of certain North Ameri- 

 can plants and animals, it has been almost positively demonstrated 

 that they are exclusively confined to regions over which similar 

 conditions prevail. In some cases the primary life areas are char- 

 acterized by the prevalence over them of entire families or genera, 

 while in the case of the minor or faunal areas the prevalence of 

 certain species or subspecies and, equally important, the absence 

 of others characteristic of other areas, are links in the chain of 

 evidence by which we are enabled to map the limits of these 

 divisions. 



The change from one area to another is not at all abrupt, l)ut 

 instead as we near their common boundar}'^ we fiud species common 

 to both occurring on the same grounds. In such cases, the preva- 



