122 Adams, Ecological Succession of Birds. [\nril 



3. Inland birds. 



Those frequenting deserts, grass lands and forests. 



Of course these ecological classes are not sharply defined, and yet 

 they are so distinct that they can be easily recognized. It should be 

 noted that the above groups are closely correlated with certain 

 dominant physical features of the earth — the sea, the shore and 

 the inland environments. 



The relative abundance and dominance of these classes of birds 

 will be determined largely by the dominance of such physical con- 

 ditions as most distinctly favor a particular ecological group. Thus 

 at sea the water birds are dominant; on shore, the shore birds; 

 and inland, still other kinds. The linear character of the shore 

 habitat and the adjacent breeding grounds gives it a rather unique 

 character, as the two other habitats occupy large expanses. How- 

 ever, the swampy, somewhat shore-like conditions of the far north 

 most nearly approach, for the shore birds, the expansive character 

 so usual for water bodies and inland areas. 



In the present discussion the emphasis placed upon the inland 

 vegetation does not mean that the dominance of other influences is 

 not recognized, but simply that it makes a convenient and fairly re- 

 liable index to many other environmental influences, as, for example, 

 the climate and topography. A further important advantage of 

 the plant index is that the science of plant ecology and many of its 

 general principles and methods are applicable to birds. A general 

 knowledge of plant ecology is therefore becoming one of the most 

 valuable tools in the hands of the field ornithologist. Every field 

 naturalist has observed the general correlation of certain birds with 

 certain kinds of vegetation. This relation is clearly expressed by 

 RidgT^^ay ('89, p. 8) as follows: "There is probably no better index 

 or key to the distribution of birds in any country than that afforded 

 by the character of the vegetation; should this vary essentially 

 within a given area, a corresponding difference in the bird-life is a 

 certainty." This phase of the subject clearly illustrates the oft- 

 repeated experience of naturalists that in order to thoroughly un- 

 derstand one subject — perhaps the favorite one — it becomes 

 necessary to study another, or even several. Thus in order to 

 know the bird life of a region it has become necessary to study the 

 ecological relations of its vegetation. 



