^°1908^^1 Adams, Ecological Succession of Birds. 113 



II. Representative Literature on Habitats and Succession. 



1, Habitat Preference. The American literature on habitat 

 preference and succession, as a subject of special investigation, is 

 very limited. By succession is meant the change or replacement 

 at a given place of one or several species (an association) by others; 

 as when a swamp is invaded by a dune and the representative swamp 

 birds are replaced by those of the dune; or even again when the 

 dune becomes fixed by vegetation and is inhabited by still another 

 association of bird life. This is a much neglected subject; however, 

 isolated observations on habitats are abundant in the biographies 

 of the various species. The fragmentary character of these biog- 

 raphies tends to make them composite and they lose what pecul- 

 iarities they may have which are due to a response on the part of 

 the bird to its particular conditions of life. These unfortunate 

 limitations clearly show that here is an extensive field worthy of 

 careful investigation. The work already done will be a useful 

 guide in many cases, but the student who wishes to develop this 

 subject must turn to the fields and forests rather than to the litera- 

 ture, both for his inspiration and his data. 



Perhaps a further word should be added concerning the limita- 

 tions of the composite life-history method, as this will aid in making 

 clear the kind of work needed in the future. This composite or 

 generalized method of describing habitats and life histories and the 

 response of birds to them, tends to lay undue emphasis upon the 

 average conditions of life and habits, and tends to neglect those 

 detailed responses to the environment which reflect the laws of local 

 influence. These results are similar to those produced by system- 

 atic students who are "lumpers" and who do not recognize local 

 races or varieties. Thus a nest may be built upon the ground at 

 the base of a shrub or bunch of grass, or in the brush, but what 

 conditions determine such sites ? In a dry meadow a Song Sparrow 

 may build directly upon the ground, but in a swamp, in order to 

 have a dry nesting site, it builds in a willow shrub. In many cases 

 the causes of these differences will be difficult to determine, but in 

 others it is a relatively simple question for any one familiar with the 

 species to solve. There are also geographic variations of habits 



