^°1908^^] Adams, Ecological Succession of Birds. 115 



dunes and beach (pp. 21, 30), yet he does not see their relation to 

 the bird Ufe in the definite way in which he sees their habitat pref- 

 erences, nor does he appear to clearly recognize the fundamental 

 relation of association within the breeding habitat. To him the 

 environment is static. However an excellent feature of his work 

 is the record of seasonal changes in the bird life of the various 

 habitats. In this connection attent^ion should be called to certain 

 papers which will greatly aid in the study of the d}Tiamics or 

 changing environmental factors w^hich influence sea or lake shores 

 bordered by dunes and swamps; conditions represented on the 

 Massachusetts coast. Gilbert ('85) has discussed the general 

 principles and topographic features of lake shores; and Gulliver 

 ('99) the shore line of the sea. But in addition to these physio- 

 graphic forces, the vegetation also has a dominating influence 

 upon bird life. For general principles relating to this subject 

 Cowles ('01) should be consulted for his discussion of the vegeta- 

 tion of inland shores and dunes, and Ganong ('03 and '06) for his 

 treatment of the Atlantic coastal conditions. These authors dis- 

 cuss the succession of the vegetation, a factor of the utmost 

 importance in the study of avian succession. 



While considering Townsend's results, it may be well to outline 

 briefly a general succession of bird life along the shore as indicated 

 by his records. It is evident from the map accompanying his 

 volume that the currents and waves are constantly modifying the 

 coast line and forming spits, bars and islands; and that the barrier 

 beach area is increasing, and thus tending to become continuous at 

 the expense of some of the ocean habitat. As the continuity of the 

 beach develops, the area of swamp land behind it tends to increase 

 and thus to further restrict the open water and increase the swamp 

 habitat. The beach sands, once free from the waves or ground 

 water, are caught up by the winds to form dunes, and may migrate 

 into the swamps and thus transform them. Thus with the exten- 

 sion of the beach the sea birds are replaced in dominance by the 

 shore birds, and a succession is produced. 



In a similar manner the dunes encroach upon the swamp, and 

 swamp birds are succeeded by those of the dunes. As the wandering 

 dunes become anchored by vegetation and forests grow upon them, 

 still other birds will invade them. Thus all stages may be expected, 



