124 MICHIGAN SURVEY, 1908. 



jects which can only be worked out in detail when local studies give 

 proper attention to local environmental responses. 



In the following account of the literature no attempt is made at 

 completeness, but the papers cited are believed to be representative. 

 These papers will help to give some idea of the kind of observations 

 and records already made, and will be suggestive as to future work. 

 Mention will first be made of the literature on habitat preference, and 

 then of that on succession. 



Br far the best discussion we have found on habitat preference of 

 the birds of a given region is that by Townsend ('05) on Essex County, 

 Massachusetts. The primary avian environments are described, the 

 representative birds listed, and their preferred habitats are briefly dis- 

 cussed. Thus, the ocean and its birds, the sand beach and its birds, 

 tlie sand dunes and their birds, the salt marshes and their birds, and 

 the fresh marshes and their birds, give a general idea of the subjects 

 treated. Regarding the birds of the sand beaches, he remarks : "Among 

 the Plover, the Black-bellied, Semi-palmated, and Piping Plovers are 

 above all birds of the beach, although the first two are occasionally 

 found in the marshes, while the last-named rarely strays from the beach 

 and the adjoining sand dunes. The Golden Plover, although at times 

 found on the wet sands, is much more likely to hunt for food on the 

 dry sands above the highest tides, or still farther inland, while the 

 Killdeer generally avoids the beach altogether, preferring the fields" (p. 

 21). And regarding the birds of the sand dunes he remarks : "Savanna 

 Sparrows nest in numbers at the foot of clumps of tall beach grass 

 throughout the dunes, and on the edges of the tidal inlets from the 

 marsh. The nests of the Eed-winged Blackbirds and the Bronzed Crack- 

 les are abundant in the bogs and groves of the birches. The' Crow, 

 in the absence of tall trees, builds perforce in the stunted pines and 

 -birches, at times only ten or twelve feet from the ground" (p. 34). In 

 the case of the Crow, note that he records the response to the dune 

 environment. 



While Townsend recognizes changes in the environment, as in the 

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

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

 erences, nor does he appear to clearly recognize the fundamental re- 

 lation of association within the breeding habitat. To him the environ- 

 ment 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 attention should be called to certain papers which will 

 greatly aid in the study of the dynamics or changing environmental 

 factors which 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 ad- 

 dition to these physiographic forces, the vegetation also has a domlinat- 

 ing 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 discuss 



