226 Nichols, Warbler Problems. [April 



First what advantage to the race can there be in the evolution 

 of so many species of similar habits? Probably though in the 

 main not unlike, a careful comparative study of the species will 

 show that sufficient difference of habit accompanies each to make 

 it fit a slightly different niche in the environment. I mention a 

 single phase, the construction of the nest. For my data on warbler 

 nests I am indebted to Mr. P. B. Philipp of New York, who pos- 

 sesses a very complete personally collected series of these. In his 

 collection we have together verified interesting points that he has 

 learned, and also worked out other matters. 



The nests of different species of Dendroica, even when found in 

 the same country, are remarkably distinct and can usually be 

 recognized at a glance. In Northumberland County, New Bruns- 

 wick, a locality with which Mr. Philipp is particularly familiar, 

 Cape May, Yellow, Black-throated Blue, Myrtle, Magnolia, Bay- 

 breasted, Blackpoll, Blackburnian, Black-throated Green, and 

 Yellow Palm Warblers all breed, and he has found the nests of all 

 but the Blackburnian placed in spruces at different heights. The 

 nest of the Blackburnian has not been found here, but doubtless is 

 placed high up in the spruces, as he has found it in such situations 

 in Pennsylvania. The Yellow Palm Warbler usually nests on the 

 ground in moss or dead ferns, but one nest was placed a few inches 

 from the ground in a small spruce. Though a single nest of the 

 Yellow Warbler was found in a spruce, that species may nest more 

 commonly in the willows. Cape May, Myrtle, and Blackburnian 

 W 7 arblers nest high, the other species low. 



The nest of the Black-throated Blue has a characteristically pale 

 exterior, weed stems, pale bark, and rotten wood-chips being favor- 

 ite materials for the bird to use in its construction. It is lined with 

 black, hair-like, slightly crinkly substance, much used for that pur- 

 pose by Warblers, the stem of a woodland ground-moss (the Cape 

 May has been seen gathering this material). Occasionally horse- 

 hair is substituted for it. In the Black-throated Green, spruce 

 twigs and birch-bark whorls are characteristic of the exterior; 

 hair and an occasional feather, of the interior. The Myrtle and 

 Blackpoll both line the nest heavily with feathers; but the exterior 

 is very different in the two, — in the Myrtle compact, of spruce 

 twigs and fine dry grass, in the Blackpoll loose and balky, rotten 



