﻿BIRDS OF PREY. TYPICAL OWLS. 325 



different primary groups will repose upon the greater 

 or less development and modification of these organs. 

 Upon this principle we find that the divisions of the 

 Strigidce, made by modern ornithologists, can all be re- 

 ferred to one or other of the following groups : — 

 1. Typical Owls, having the facial disk very large and 

 complete, with large ears and (in general) an ample 

 operculum ; 2. Horned Owls, furnished with egrets, 

 and a large facial disk, but having only small or mode- 

 rate sized ears ; and 3. Diurnal or Hawk Owls, where 

 the conch of the ear is comparatively small, and is 

 destitute of an operculum : the head has no egrets, and 

 the facial disk is imperfect or obsolete. The reader will 

 be at no loss to perceive in the first the characters of 

 the typical group ; in the second, the sub-typical ; and 

 in the third the aberrant. Let us now consider each of 

 these separately. 



(26l.) The strigin^e, or typical owls, are well re- 

 presented by the common white species of this island. 

 The head is uncommonly large, and the facial disk of 

 great circumference ; the extent of the latter is marked 

 by a dense semicircle of rigid narrow feathers, form- 

 ing a sort of collar, and of which the ends are turned, 

 lying close upon each other in the manner of scales. 

 The aperture of the ear, which is within this collar, is 

 large, measuring in the brown owl more than an inch 

 in length. This is protected by an operculum, which 

 is sometimes much larger (as in Stria? flammea) than 

 the aperture, and sometimes nearly of the same size. 

 These differences, however, will not be regarded at pre- 

 sent as generic. Owls of this group are eminently 

 nocturnal, and their geographic distribution, as is usual 

 in all pre-eminent types, is very wide ; the white owl, 

 under slight variations of colour, having been found 

 over all the temperate parts of America, in the sultry 

 groves of India, and even in Australia. Without at- 

 tempting, for the present, to arrange the sub-genera 

 of this group in their natural order of succession *, we 

 * This is a task of very peculiar difficulty, for it is frequently impossible 

 Y 3 



