ORDER INSESSORES, OR PERCHERS. 423 



within the Owl family. In the character of its plumage, also, 

 it bears a resemblance to the Diurnal Birds of Prey ; and like 

 them, it dashes boldly on its victim, and seizes it on the wing, 

 instead of stealing noiselessly upon it. In summer it feeds prin- 

 cipally on mice and insects ; but in the snow-clad regions which 

 it frequents in winter, neither of these are to be procured, and it 

 then preys mostly on Ptarmigan, the flocks of which are 

 followed by it, in their spring migrations to the northward. 

 Nearly allied to this species, which is about fifteen inches in 

 length, are several others ; which inhabit different portions of 

 the globe, and present slight variations in structure and habit. 

 One of these, a native of Northern Asia, is but little inferior to 

 the Snowy Owl in size. 



ORDER II. INSESSORES. 



384. The group of Perching Birds, included in this order, 

 is the most numerous and the most varied in the whole class. 

 It comprehends all those tribes which live habitually among 

 trees, with the exception of the Rapacious Birds on the one 

 hand, and the Climbing Birds on the other. From the former 

 they are sufficiently distinguished, by the absence of those 

 characters which have been mentioned as peculiarly marking the 

 Birds of Prey ; and from the latter they are at once known by 

 the position of the toes. For in all the true Insessorial Birds, 

 the toes are three before and one behind (Fig. 205); whilst in 

 the Scansores, two of the toes are directed backwards (Fig. 187). 

 The adaptation of the foot of this order to grasping or perching, 

 is evident from the situation of the hinder toe ; which is in- 

 variably placed on the same level with those in front, and thus 

 distinguishes the Perchers from the Gallinaceous and Wading 

 Birds. These Birds pass the greater part of their time on the 

 wing, and only use their legs as an occasional support ; these 

 members are consequently short and weak, in comparison with 

 those of most of the other orders. The toes are slender, flexible, 

 and of moderate length ; with long, slender, and slightly-curved 



