NORTH AMERICAX BIRDS. 



Family STRIGID^. — The Owls. 



CnAH. Ej'es directed forwani, ami .siiiniinidcd by a radiating system of feathers, 

 which is bounded, except anteriorly, by a nill of .^till', compactly webbed, differently 

 lbrm<'d, and somewhat recurved feathers ; loral feathers antrorsc, long, and dense. 

 Plumage very soft and la.x, of a line down}' texture, the feathers destitute of an 

 after-shaft. Oil-gland without the usual circlet of feathers. Outer webs of the quills 

 with the points of the libres recurved. Feathers on the sides of the forehead frequently 

 elongated into ear-like tufts ; tarsus usually, and toes frequently, densely feathered. Ear- 

 opening very large, sometimes covered by a lappet, ffisophagus destitute of a dilated 

 crop ; cojca large. Maxillo-palatines thick and spongy, and encroaching upon the 

 intervening vallej' ; basipterygoid processes always present. Outer toe reversible ; pos- 

 terior toe only about half as long as the outer. Posterior margin of the sternum doubly 

 indented ; clavicle weak and nearly cylindrical, about equal in length to the sternum. 

 Anterior process of the coracoid projected forward so as to meet the clavicle, beneath the 

 basal process of the scapula. Eggs variable in shape, usually nearly spherical, always 

 immaculate, pure white. 



Tlie Owls constitute a very natural and sliarply limited family, and though 

 the species vary almost infinitely in tlie details of their structure, they aU 

 seem to fall within the limits of a single subfamily. 



They have never yet been satisfactorily classified, and all the arrange- 

 ments which have been either proposed or adojited are refuted by the facts 

 developed upon a close study into the true relationship of the many genera. 

 The divisions of " Night Owls," " Day Owls," " Horned Owls," etc., are 

 purely artificial. This family is much more homogeneous than that of the 

 Falconulw, since none of the many genera whicli I have e.x^amined seem 

 to depart in tlioir structure from the model of a single subfamily, though a 

 few of them are .somewhat aberrant as regards peculiarities in the detail of 

 external form, or, less often, to a slight extent, in their osteological char- 

 acters, tliougii 1 liave e.xamined critically only the American and Europeau 

 species ; and there may be some Asiatic, African, or Australian genera 

 wiiich depart so far from the normal standard of structure as to necessitate a 

 modification of this view. In the structure of the sternum there is scarcely 

 the least noticeable de\-iation in any genus ^ from the typical form. The 

 appreciable differences appear to be only of generic value, such as a different 

 proportionate length of the coracoid bones and tlte sternum, and width of 

 the sternum in proportion to its length, or the height of its keel. The crania 

 present a greater range of variation, and, if closely studied, may afford a 

 clew to a more natural arrangement than the one which is here presented. 

 The cliief differences in the skulls of different genera consist in the degree 

 of pneumaticity of the bones, in the form of the auricular bones, the com- 

 parative length and breadth of the palatines, and very great contrasts in the 



' I have, howcvpr, ex.imini'd tlic .sterna only of Xiidca, Ditbo, Olus, Bnichijoliis, Syrnium, 

 Nyclale, and Glaucidium. 



