120 Adams, Ecological Succession of Birds. [April 



succession which have been discussed by a few authors. These 

 subjects have either been discussed in a very general manner or are 

 detailed discussions of special regions or groups of plants and 

 animals. For this reason, perhaps, their bearing upon other groups 

 than those specifically mentioned are very likely to .be overlooked 

 by those who take little interest in any subject or discussion which 

 does not specifically mention their specialty or locality. This phase 

 is mentioned in order to show that while avian successions have 

 been considerably neglected, advances have been made elsewhere, 

 by means of which some general principles appear to have been 

 fairly well established. This is particularly true of plant succes- 

 sion, as shown by the writings of Cowles ('01), and in considerable 

 detail by Clements ('05). The discussion by Clements will be 

 particularly valuable to the student of avian succession. 



III. The Major Avian Environments. 



As has been seen in the preceding review of the literature on 

 haunts, no comprehensive discussion has been given of the environ- 

 mental influences or ecological distribution of (extra-tropical) North 

 American birds. Various authors have discussed their geographic 

 distribution, and certain geographic variations have been referred 

 to certain environmental influences, but a general ecologic treat- 

 ment, as contrasted with a primarily faunistic one, has not been 

 made. This is remarkable when we recall the fact that the collec- 

 tions of North American birds are, considering the large area con- 

 cerned, the best in the world both as to quality and as to quantity 

 (Stejneger, '03). This means that there have been many trained 

 collectors; but what has become of the notes and observations on 

 the environments and conditions of life of these birds, which must 

 necessarily have been known to successful collectors? Part of 

 these observations have been published, and perhaps no one is to 

 blame because more have not; but the point of significance is that 

 we have, in fact, hardly made a beginning in the careful detailed 

 study of the bird environment and its development as a distinct 

 field of study. In common with the remainder of the North Ameri- 

 can biota, several general principles are known, but they do not 

 appear to be current among ornithologists. 



