166 NEW YORK ZOOLOGICAL SOCIETY. 



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 dowai 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 stififer 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 leg. 



PART II.— SPECIAL ACCOUNT. 



The group of owls is, as a whole, so homogenovis 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 



