574 EAPTORES, OE BIEDS OF PEEY. 



Nocturnal Birds or Prey. 



Nocturnal birds of prey are distinguished by large staring eyes, 

 directed straight in front, and surrounded by a circle of slender 

 and stiff feathers, which, by their circular radiation round the 

 face, form a nearly complete disk, to which the name bifacial disk 

 has been given ; by the large development of their head ; by very 

 short bills, devoid of cere, which is replaced by a plain skin covered 

 v/ith hairs ; by tarsi feathered down to the claws ; by the mobility 

 of the outside toe, which can be turned either forwards or back- 

 wards; by very strong, sharp, and retractile claws; by abundant 

 and soft plumage ; and by tails which are generally short. 



But the original characteristic of these birds, and that which 

 has contributed to their union in one group, is their inability to 

 bear the light of mid-day, and the faculty they possess of being 

 able to see in twilight, owing to the pupils of their eyes having 

 enormous powers of dilation. They therefore remain hidden in 

 their retreats while the sun is high, and do not begin to hunt until 

 the luminary has approached the horizon, when they are able 

 to distinguish with surprising clearness the objects on which they 

 prey. 



We are not, however, bound to believe that these birds can see 

 in the midst of perfect darkness. When the night is thoroughly 

 obscure they again become subject to the law common to all. The 

 epithet of " nocturnal," which is applied to them, is, therefore, not 

 strictly accurate, and must not be taken literally. They manifest 

 the greatest amount of activity when the moon diffuses her light 

 over the earth ; then it is that they revel in their destructive 

 instincts, levying a heavy tax on all weaker animal life. 



The Raptores have the sense of hearing strongly developed, 

 owing to the large cavities existing in their skulls, which com- 

 municate with the internal ear, and thus increase the capacity of 

 this organ. 



Their plumage is streaked with diversely- arranged markings, 

 and is quite as soft and delicate as the down of fledglings. These 

 peculiarities are probably owing to the special conditions of their 

 existence. Constantly deprived as they are of the rays of the 



