OWL 675 



ment of conch, which may perhaps be accounted for by the 



ordinary prey of the bird being the larger rodents, that from their 



size are more readily seen, and hence 



the growth of the bird's auditory 



organs has not been much stimulated. 



In Strlx (as the name is here used), 



a form depending greatly on its sense ~^^'^^^'^^^':il'(lW>^^S 



of hearing for the capture of its prey, '^' *'*^*^*' 



the ear-conch is much enlarged, and ^'^^ ^""^ "^^^ °^ ^"''°- 



. 1 1 n (After Swainson.) 



it has, moreover, an elevated flap or 



operculum. In Asio^ containing the Long-eared and 8hort-eared 

 Owls of Europe, Asia and America, the conch is enormously exag- 

 gerated, extending in a semicircular direction from the base of the 

 lower mandible to above the middle of the eye, and is furnished in 

 its whole length with an operculum.^ But what is more extraordinary 

 in this genus is that the entrance to the ear is asymmetrical — the 

 orifice on one side opening downwards and on the other upwards. 

 This curious adaptation is carried still further in the genus Nydala, 

 containing two or three small species of the Northern hemisphere, 

 in which the asymmetry that in Asio is only skin-deep extends, in 

 a manner very surprising, to several of the bones of the head, as 

 may be seen in the Zoological Society's Proceedings (1871, pp. 739- 

 743), and in the large series of figures given by Messrs. Baird, 

 Brewer and Ridgway {N.-Am. Birds, Hi. pp. 97-102). 



Among Owls are found birds which vary in length from 5 

 inches — as Glaucidimn cohanense, which is therefore much smaller 

 than a Skylark — to more than 2 feet, a size that is attained by 

 many species. Their plumage, none of the feathers of which pos- 

 sesses an aftershaft, is of the softest kind, rendering their flight al- 

 most noiseless. But one of the most characteristic features of this 

 whole group is the ruff, consisting of several rows of small and 

 much-curved feathers with stiff shafts — originating from a fold of 

 the skin, which begins on each side of the base of the beak, runs 

 above the eyes, and passing downwards round and behind the ears 

 turns forward, and ends at the chin — and serving to support the 

 longer feathers of the "disk" or space immediately around the 

 eyes, which extend over it. A considerable number of species of 

 Owls, belonging to various genera, and natives of countries most 

 widely separated, are remarkable for exhibiting two phases of colora- 

 tion — one in which the prevalent browns have a more or less rusty- 

 red tinge, and the other in which they incline to grey. Another 

 characteristic of nearly all Owls is the reversible property of their 

 outer toes, which are not unfrequently turned at the bird's pleasure 



^ Figures of these different forms are given by Macgillivray {BrU. Birds, iii. 

 pp. 396, 403, and 427), and of Asio otus in tlie Fourth Edition of Yarrell's British 

 Birds (i. p. 162). 



