166 NEW YORK ZOOLOGICAL "SOCIE I: 
As illustrating adaptative radiation among these birds we may 
consider three types of feet. The foot of the barred owl is typical 
of the owls in general. It is feathered down the entire length of 
the tarsus or lower leg and even to the distal joint of the toes. 
The talons are long, sharp and curved and the soles of the feet 
are covered with rough dermal spicules which must be of great 
assistance in keeping a firm hold upon living prey. 
The foot of the snowy owl shows a beautiful adjustment to life 
in the treeless regions of the far north, closely paralleling the 
foot of the ptarmigan. The entire foot to the very base of the 
claws is completely hidden in a dense growth of loose-vaned 
feathers, and even the soles of the feet are thus covered, the 
feathers here being stiffer and more bristle-like. When, for 
months at a time, the rocks and tundras are covered deeply with 
snow, the owl is thus protected from the cold, frozen surfaces on 
which it must perch and roost. The dead, non-conducting pad of 
feathers on each sole, leaves exposed nothing but the horny tips 
of the claws. 
On our western prairies the little burrowing owls have broken 
away from all traditional owl customs, and have taken to a 
diurnal life and a subterranean home. Under these conditions, 
feet like those of other owls would be almost useless, and so we 
find a radical change in these members. The tarsus is much 
elongated as may be realized by a comparison between a great 
horned and a burrowing owl. While the former may have as 
much as thirty-five inches greater extent of wing, yet there is 
but one-half inch difference in the length of the tarsal joint of 
the les: 
PART IIT—SPECIAL ACCOUNT. 
The group of owls is, as a whole, so homogenous and the radia- 
tions within the Order so uniformly distributed that the general- 
izations of Part I, while true of the owls of the world, may, with- 
out exception, be applied to the owls of the Nearctic Region. This 
Region comprises the North American continent south to, and 
including, the high, central tablelands of Mexico. Its boun- 
daries are determined by the limits of distribution of many im- 
portant groups of plants, insects, birds, mammals and other forms 
of life. The remainder of the Western Hemisphere comprises 
what is termed the Neotropical Region. 
In this Nearctic Region we find twelve well-marked groups or 
