

212 FAUNAL DIVISIONS OF EASTERN NORTH AMERICA. 



canus) , the lynx (Lynx canadensis) , the fisher (Mustela pennanti) , the red squirrel 

 (Sciurus hudsonicus), and the woodchuck (Arctomys monax), while among birds 

 the Barren Ground species above mentioned breed within its confines, and the 

 Bohemian waxwing (BombyciUa garrula), the northern shrike (Lanius borealis), 

 the rosy finch (Leucosticte tephrocotis) , the orange-crowned warbler (Vemivora 

 celata), yellow warbler (Dendroica cestiva), myrtle warbler (D. coronata), black- 

 poll warbler (D. striata), Wilson's warbler (Wilsonia pusilla), and the gray- 

 cheeked and BicknelTs thrushes (Hylocichla alicice and H. a. bickneli), the olive- 

 backed thrush (H. ustulata swainsoni) and the Alaska hermit thrush (H. g. 

 guttata) extend their breeding range into it to a greater or less extent. 



II. The Atlantic Forest Fauna. 



The vast forested region of northeastern, north central, and northwestern 

 North America that stretches from the Atlantic border to Alaska. The drainage 

 of this great area is into the Atlantic and Arctic Oceans. Its northern portion 

 is mainly a growth of conifers which fade away on the northern border into the 

 tree-limit belt. This, the Coniferous Forest Type of fauna, is equivalent to the 

 Boreal Zone and the Canadian Fauna of authors. South of this the evergreens 

 give place to a mixed forest of deciduous hardwood species — oaks, ashes, elms, 

 maples, birches, beeches, aspens, and numerous other kinds, its fauna forming 

 the Deciduous Forest Type. This is the equivalent of the Transition Zone and 

 the Alleghanian Fauna of writers. The difference observed by Merriam as to 

 the temperature data between his Transition and Boreal Zones represents an 

 undoubted causative element in the differentiation of the forest into its two 

 types. It seems hardly credible, however, to suppose that this temperature 

 difference has affected each organism of its fauna so profoundly as to produce a 

 barrier. The fauna is essentially part of the forest, and its history and develop- 

 ment pertains directly to the history and spread of this forest during the post- 

 glacial period. A well-marked " forest fauna' ' is recognized as having existed 

 during the last glacial retreat, following a tundra or arctic fauna, the remnant 

 of which last is seen in the present Sub-Arctic Fauna as above described. 1 



(a) The Coniferous Forest Type— The history of this f aunal type is coincident 

 with the spread of coniferous forests over a wide tract of country left bare by 

 the shrinking of the ice-sheets at the close of the last glacial period (Wisconsin 

 Stage). The fauna is characterized by its decided palearctic affinities. Like 

 the Sub-Arctic Fauna, into which it merges along the tree-limit, many of its 

 characteristic forms are but slightly differentiated from those of the Eurasiatic 

 continent. Among mammals this palearctic element is found in such species as 

 the moose (Alces), the wapiti (Cewus) } the caribou (Rangifer), the black bear 

 (Ursus), and others, while among birds such genera as Otocoris, Corvus, Pinnem, 

 Loxia, Carpodacus, Acanthis, Plectrophenax , Calcarius, Lanius, BombyciUa, 

 Riparia f P etrochelidon y Hirundo, Anthus, Certhia, Sitta, Penthestes, Regulus, ana 

 Planesticus are undoubtedly of palearctic origin. 



1 Osborn, The Age of Mammals, New York, 1910, p. 435. 



