^'°1908^^] Adams, Ecological Succession of Birds. 135 



Little is gained by sharply segregating the marsh and shore birds, 

 although the marsh birds show a preference for conditions better 

 represented or correlated with topographically older coasts, pro- 

 tected and inland conditions. Attention should be directed, how- 

 ever, to the significant fact that successions initiated with such 

 diversity will produce a variation in the composition of the associa- 

 tions. Also that so far as possible these variations should be con- 

 sidered comparatively and synthetically in reconstructing and 

 anticipating successions. 



The American Bittern, Lesser Yellow-legs, Swamp Sparrow 

 and Marsh Hawk belong to this society of marsh birds. As in the 

 case of the aquatic association, these birds generally nest in close 

 proximity or entirely within these shore or marsh conditions. Still 

 other species frequent this belt to feed, as it is an open area; but 

 their presence is mainly conditioned by the adjacent shrubs or 

 forest. The very limited number of species in the aquatic and 

 shore associations is worthy of particular mention. 



The Yellow-legs, Spotted Sandpiper, Bittern and Marsh Hawk 

 range far to the north, even to the Barren Grounds, and thus suggest 

 chances, as in the case of the aquatic association, of an early arrival 

 and succession upon the island. 



With the growth of the island, there has been a corresponding 

 extension of the outer and inner shore habitats, although the 

 encroaching vegetation has had a marked tendency to restrict the 

 area of the inland habitat. The dominant environmental influences 

 in this habitat appear to be, 1, the physical character of the shore 

 and beaches; 2, the dynamic forces of the water bodies and streams; 

 3, the encroachment of the vegetation; 4, the downward migration 

 of the shore; and 5, the habits and structure of the birds. 



As a general rule, we may say that the beach of the outer lake 

 tends to be succeeded by either the bog or upland associations, and 

 those inland by the bog association. 



c. Bog-forest Association and Habitat. 



As just stated the outer coast or an inland one may develop into 

 a marsh or bog habitat or association. In the bog, the Tamarack, 

 Black Spruce and Arbor Vitse are the pioneer trees in transforming 



