216 The Bird 



their cackling and beating their wings, they roused Mar- 

 cus Manlius, a brave soldier and formerly consul, who, 

 snatching up his arms and giving the alarm, flew to the 

 ramparts, set upon the Gauls, and by precipitating one 

 of them over the rocks terrified the rest so much that 

 they threw down their arms." So also Pliny, ^Elian, and 

 Columella vaunt the hearing of Geese. But leaving leg- 

 endary lore, it is certain that birds would not have the 

 power of producing the most varied as well as the sweet- 

 est sounds in all Nature, had they not been provided 

 with powers of hearing, correspondingly acute and dis- 

 criminating. 



The organ of hearing is complicated and there are 

 many points about it which are still mysteries to scientists. 

 The flap of skin to which we give the name of ear is 

 entirely absent in birds, and indeed in ourselves is a very 

 unimportant part of the auditory apparatus, serving 

 only as a collector of sound-waves. The opening of the 

 inner ear on each side ol the head, in birds, is usually 

 protected by a cover of feathers which are bristle-like, 

 partly denuded of barbicels, doubtless to avoid any muf- 

 fling of sound-waves. In owls this opening is of very 

 large size and protected by a movable flap of skin which 

 may serve to aid in focussing the sounds from below 

 a very useful function to an owl at night, silently wing- 

 ing its way over field and meadow in search of mice and 

 other terrestrial prey. A rather singular fact is that in 

 many owls the two ear-openings are unlike, one being 

 larger and of a different shape from the other, and this 

 asymmetry extends even to the form of the skull itself. 



