ANDER.SON — THE BIRDS OF IOWA. 141 



eastern states is the large percentage of clear skies in the winter 

 season. . . . For the year the average of the state is as follows: 

 156 clear, 107 parti}- cloudy, and 102 cloudy days." 



FAUNAI, AREAS. 



Dr. C.^Hart Merriam has shown 1 that the continent of North 

 America is divided into three primary life region.s — Boreal. Aus- 

 tral, and Tropical — each of transcontinental extent. Their bound- 

 aries are sinuous, conforming to the distribution of temperature. 

 The Austral region is likewise sub-divided into three transconti- 

 nental zones: (i) a Transition zone; (2) an Upper Austral zone; 

 (3) a Lower Austral zone; each of which may be sub-divided in 

 an east and west direction into two or more areas, some of which 

 are based on humidity instead of temperature. The eastern ends 

 of these three belts have long been recognized by zoologists, and 

 are known as the Alleghanian, Carolinian, and Austroriparian 

 faunas. Dr. Merriam' s map included the greater part of Iowa in 

 the Carolinian fauna, an eastward exten.sion or loop of the Great 

 Plains fauna covering the northwestern corner of the state and part 

 of southwestern Minnesota. 



In a later paper- Dr. Merriam maps the northern boundary of 

 the humid division of the Upper Austral (Carolinian) fauna as 

 passing from central South Dakota across southwestern Minne- 

 sota, crossing the western part of the Iowa-Minnesota line, dip- 

 ping down into Northern Iowa, crossing the Minnesota line again 

 not far from the Mississippi, following the Mississippi bottoms a 

 short distance into southeastern Minnesota, passing down across 

 the southwestern corner of Wisconsin, extending a small loop 

 into northern Illinois, then passing some distance up along the 

 lake shore in southeastern Wisconsin. The eastern or humid 

 division of the Transition (Alleghanian) zone covers only a small 

 strip in the extreme northern part of Iowa, not more than two or 

 three counties deep in its widest portion, extending from about 

 the western third of the state line almost to the Mississippi River. 



In "the eastern humid or Alleghanian area . . . the chestnut, 

 walnut, oaks and hickories of the south meet and overlap the 



1. "The Geographic Distribution of Animals and Plants in Nortli America." Year- 

 book of the U. S. Department of Agricnlture. 1894. Pp. 303-214. 



2. Bulletin No. 10. U. S. Dept. of Agriculture. Division of Hiological Survey. I,ife 

 Zones and Crop Zones of the United States. Hy C. Hart Merriam, Chief, Biological Sur- 

 vey. Washington: Government Printing Oflfice. 1S9S. 



[Proc. D. A. S., Vol. XI. J 21 [August 8, 1906.] 



