^"l908^^] Adams, Ecological Succession of Birds. 147 



more rapid advance along evolution aiy lines is in a large measure 

 due to the almost utter failure to analyze d}Tianiically environmen- 

 tal complexes. Succession, studied in its broader aspects, should 

 greatly aid in the formulation of the laws governing the "struggle 

 for existence," which is frequently condemned for its indefinite 

 character. 



From another point of view there are very important reasons for 

 urging extensive studies of this character at a relatively early date, 

 because the encroachments of civilization, which by the destruction 

 of the forests, the drainage of the land, irrigation, farming and 

 grazing of the grasslands, are rapidly destroying original environ- 

 mental conditions before they are studied ecologically. Much of 

 Europe has already gone through this stage of demolition, and it 

 is only to new and relatively unmodified countries that we can look 

 for an adequate statement of these problems and their relations 

 in their original and primarily evolutionary and developmental 

 form. It is not improbable that the next generation may wonder 

 why some subjects, the investigation of which might have been 

 delayed, have received detailed attention, while others equally or 

 perhaps even more important have been almost ignored and must 

 forever remain unknown because of this neglect to .secure the "van- 

 ishing data." (Cf. Haddon, '03.) 



Such ecological studies may be ex]:)ected to have a valuable reflex 

 influence upon the naturalist himself. AYe may hope that the 

 future revisor of a group of birds will consider a knowledge of the 

 field relations of his specimens as an essential qualification, just 

 as at the present time a large series of specimens is held necessary. 

 Fifty years ago a limited series was considered no disqualification, 

 just as to-day the lack of a knowledge of their ecological relations 

 is not so considered. Perhaps our ideas of relative values must 

 change. In this connection a statement from Tristram ('94, p. 472) 

 is to the point: — "The closet systematist is very apt to overlook 

 or take no count of habits, voice, modification and other features 

 of life which have an important bearing on the modification of 

 species. To take one instance, the short-toed lark {CalandreUa 

 brack ydacti/la) is spread over the countries bordering on the Medi- 

 terranean ; but along with it, in Andulusia alone is found another 

 species, Cal. haetida, of a rather darker color, and with the second- 



