^'ij^P 1 ] Tkotter, Land-Bird Fauna of X. E. America. 231 



territory, while the Carolinian birds are the laggards in this north- 

 ward movement. Each group or fauna has become more or less 

 adapted to certain characteristic conditions within the area in 

 which they have established themselves as breeders. Some of 

 the Carolinian species, as the Cardinal, the Carolina Wren, the 

 Tufted Titmouse, and the Turkey Buzzard show but a slight 

 tendency to recede from their breeding range during the winter, 

 owing, no doubt, to the less northerly position which they have 

 attained. Toward the northwest where a wide expanse of territory 

 has been open since the Glacial Period many species of birds 

 which breed widely throughout the Transition zone have spread 

 as far north as the Great Slave Lake, reaching even to the edge of 

 the Barren Grounds. 1 



The problem as to the primitive centers of distribution from 

 which our bird fauna was originally derived has been so ably set 

 forth by Dr. J. A. Allen in his article on ' The Geographical Origin 

 and Distribution of North American Birds, considered in Relation 

 to Faunal Areas of North America', 2 that there is little left to say 

 upon the subject. Students of ornithology and of geographical 

 distribution in general owe Dr. Allen a lasting debt of gratitude 

 for his comprehensive presentation of the facts and his illumi- 

 nating deductions therefrom. It would appear from Dr. Allen's 

 review that sometime during the Tertiary Period, possibly as early 

 as the late Miocene, there was a spreading out toward the east of 

 certain types of birds which find their center of development to-day 

 in the Plateau Region of southwestern North America and Mexico. 

 Such forms as the Chewink, the Thrasher, and the Bluebird are 

 certainly of plateau origin and the same is probably true of the 

 Bob-white and the Wild Turkey. A second and large element in 

 our eastern bird fauna is of tropical origin, derived from Middle 

 and South America. To quote Dr. Allen 3 : "Our Vultures, several 

 genera of our Hawks and Owls, our Cuckoos, most of our Wood- 

 peckers, our Nighthawks, Whippoorwills, Swifts, and all of our 

 Hummingbirds; all of our Flycatchers, Orioles, and Blackbirds, 



1 See Preble, North American Fauna, No. 27. 'A Biological Investigation of the 

 Athabasca-Mackenzie Region.' 1908. 



2 The Auk, Vol. X, p. 97. April, 1893. 



3 Dr. Allen, in his paper, is speaking for the entire country, not the eastern part 

 alone, to which the present article is confined. 



