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 Sérix (as the name is here used), 
a form depending greatly on its sense 
of hearing for the capture of its prey, 
the ear-conch is much enlarged, and BIVESAND EAS OU BUES: 
: (After Swainson.) 
it has, moreover, an elevated flap or 
operculum. In Aszo, containing the Long-eared and Short-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 Nyctala, 
containing two or three small species of the Northern hemisphere, 
in which the asymmetry that in 4szo 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, iii. pp. 97-102). 
Among Owls are found birds which vary in length from 5 
inches—as Glaucidium cobanense, 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 
1 Figures of these different forms are given by Macgillivray (Brit. Birds, iii. 
pp. 896, 403, and 427), and of Asio otws in the Fourth Edition of Yarrell’s British 
Birds (i. p. 162), 
