^°1908^^] Adams, Ecological Succession of Birds. 117 



Yellow-throat. He has shown that different varieties have differ- 

 ent habitat preferences. Jacobs ('04) has given us an interesting 

 habitat study of a single species in Pennsylvania, the Golden-winged 

 Warbler. 



Let us now turn to another class of habitat studies, those which 

 through man's influence throw only a subordinate light upon "natu- 

 ral" habitats and succession, and are primarily of economic impor- 

 tance but contain valuable habitat data. 



An interesting and rather unique paper belonging to this class, 

 based on observations in Southeastern Michigan, is by Watkins 

 ('00). It is entitled 'Michigan Birds that Nest in Open Meadows.' 

 A few of his statements explain his point of view: "To make more 

 plain the limit and scope of this treatise, which, of necessity must be 

 longer than I hoped, I will include in my list only such species as I 

 have found nesting upon the ground in the open fields and mead- 

 ows, excluding those found nesting upon the boundary fences or 

 ground; also those nesting in the open marsh lands which are 

 undrained and boggy to the extent of being unfit for hay or pasture" 

 (p. 67). The paper contains numerous notes on the habitat pref- 

 erence and variations in these traits. 



By far the most comprehensive and thorough study of any limited 

 farm area is that by Judd ('02) of a farm in Maryland. In this 

 paper habitat preferences are clearly recognized, and discussed 

 rather fully (pp. 12-20). The birds are associated thus: — birds 

 that nest in open fields, birds that depend on covers, birds of less 

 limited distribution (consists largely of remarks on haunts), and 

 birds of varied distribution. His last two sections are rather 

 miscellaneous in character and show that the principles of classifi- 

 cation for habitats were not cleai'ly defined in his own mind. 



The only other paper discussing habitat preference in detail is 

 also the latest upon the subject, and is by Forbes ('07). This is a 

 preliminary report on a bird census across the corn belt of Central 

 Illinois in the early autumn; a study of the feeding grounds and 

 preferences as influenced by the dominant crops of the area tra- 

 versed, corn, pasture, and stubble. By means of this census, the 

 habitat preferences for different crops and the association of species 

 in them is statistically determined. The paper is particularly 

 suggestive for its bearing on the subject of dominance; however. 



