LIFE-HISTORIES 



Off 



BIRDS 



OF EASTERN PENNSYLVANIA. 



CHAPTER I. 



Subclass I. Aves Aereae, or Insessores. 

 Aerial (Birds, or (Perchers. ' 



Of the three primary divisions constituting the 

 class Aves, the above ranks as first in importance 

 and highest in position, and embraces all existing 

 species down to the GalliniB or gallinaceous birds. 

 Without entcrinsj into a full definition of its ex- 

 ternal characters, suffice it to say, that with rare 

 exceptions, the toes occupy the same plane and 

 touch the same support throughout, thus adapting 

 them for grasping or perching. The members of 

 this extensive group are now usually placed in five 

 orders of which the first is the 



Order Passeres. (Perchers proper. 

 The low insertion of the hind toe and its length; 

 its great power of opposibility to the front toes, 

 and the superior mobility of the same which is 

 secured by the separation of its principal muscle, 

 from that that flexes the other toes collectively, 

 perfectly adapt the feet for grasping. The hind 

 toe is ever present and never directed anteriorly 

 or laterally. The feet are never zygodactyle, syn- 

 I A 



