68 NEBRASKA ORNITHOLOGISTS' UNION 



the most charactei'istic breeders: Lark Bunting, Western Grasshopper 

 Sparrow, Western Vesper Sparrow, Brewer's Sparrow, Lazuli Finch, West- 

 ern Meadow-lark, Bullock's Oriole, Bronzed Grackle, Brewer's Black- 

 bird, Black-headed Grosbeak, Praii'ie Sharp-tailed Grouse, Sage Hen, 

 Long-tailed Chat, Yellow Wai-bler, Western Yellow-throat. 



Some of the larger mammals are the Antelope, the Badger, a jack 

 rabbit (Lepus inelanotis), a cottontail (Lepus baileyi), the Coyote {Canis 

 nebrascensis), the Skunk (Mephitis hvdsonica) and a bob-cat (Lynx rnfus'?). 

 Smaller f'pecies noted were Cynomys ludovicianus, Perodipus richardsoni , 

 Onychomy^ leucogaster, Perognatlms flavescens(?), P. hispidus paradoxus, 

 Mici'ottis modestus, Spermophilus t. palUdus, Peromyscus t. nebrascensis, 

 Geomys Ititescens, Thomomys sp. 



LIFE ZONES. 



From what has already been said concerning the occurrence of various 

 semi-boreal, as well as strictly austral, forms of life in northwest 

 Nebraska it is obvious that we have here at least two well-defined life 

 zones, each characterized by the possession of species of plants, birds, 

 and mammals not found in the other. To be more exact, the two sub- 

 di'S'isions of the Hat Creek Basin which I have designated as the "Sage 

 Brush Plains Region" and the "Bad Lands Area," both agree in possess- 

 ing truly arid land or desert species, able to withstand great extremes 

 of drouth and heat; Avhile distinctive forms are possessed by each 

 subdivision owing to such minor factors as variation in the amount 

 of plant growth, soil differences, and surface configuration. Thus both 

 the above subdivisions fall naturally under the arid portion of the 

 Upper Austral Life Zone, defined by Merriam as the Upper Sonoran 

 Faunal Area.* 



Again, the presence of such semi-boreal species as have already been 

 listed from the wooded canons points to at least a life zone having 

 boreal affinities. And when we take into account the presence of a 

 number of southern species, or species of southern extraction, in the 

 same region it clearly indicates a zonal area v^dth mixed affinities, partly 

 boreal and partly austral in its composition. To this zone Dr. Merriam, 

 who at the present time is unquestionably the authority on geographic 

 distribution of animal life in IN^orth America, applies the name "Transi- 

 tion" because of its intermediate position. Inasmuch as the same 

 authority has divided the Transition Zone of North America into three 

 geographic areas characterized chiefly by the relative amount of humid- 

 ity, the vs'ooded canon region together with the adjacent plateau would 

 come under the Arid Transition. 



Now that the four different regions of northwest Nebraska have 

 resolved themselves into two fairly well-defined life zones the next step 

 will be to group, as far as possible, the various plants, mammals, and 

 birds under their respective zones. 



» Life Zones and Crop Zones of U. S., 1898, p. 36. 



