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TEXT-BOOK OF ZOOLOGY 



and prying everywhere. The eyes are large and capable of receiving a 

 large number of light-rays even at night, the pupils, moreover, being 

 capable of dilating to a considerable extent. For near objects its sight is 

 excellent. It flies accordingly only at an inconsiderable height above the 

 ground, both eyes, moreover, being directed forwards, so that during flight 

 they are turned towards the ground. 



3. On pitch-dark nights, however, the owl is no more able to see than 

 any other animal, and then relies only on its sense of hearing, which is 

 of marvellous acuteness. Even when asleep the bird can hear the 

 slightest noise, whilst during the pursuit of prey not the rustle of a 

 mouse nor the quiver of a sleeping bird escapes its notice. While at 

 rest the large apertures of the ears are closed by cutaneous flaps, or 

 covers, which are turned forwards during flight. These covers act as 



receivers of sound, like the ex- 

 ternal ears (pinnre) of mammals. 

 Their surfaces are much in- 

 creased by 



4. The feathers of the disc. 

 As, however, the sound-receiving 

 flaps stand in front of the ear- 

 openings, they must naturally 

 convey to the ear chiefly the 

 sound-waves coming from be- 

 hind. The owl, therefore, gener- 

 ally hears the movement of its 

 prey when it has flown past it ; 

 then it captures it with a sudden 

 turn of its body. 



5. Its silent, light -winged 

 flight enables it to hear the slightest sound, and, moreover, prevents it 

 from being heard by its prey. This noiseless flight is due to the thick, 

 loose, silky -soft plumage. (Compare, on the other hand, the diurnal birds 

 of prey, with their stiff plumage and rushing flight.) 



Head of Barn-Owl, with the Aural Apei: 



TURES UXmVEKKJl. 



D, Ear-cover ; 0, aperture of the ear-passage. 



Related Species. 



The largest of the owl species, and the only really injurious member 

 of the family, is the Eagle-Owl (Bubo maxivuis), which occurs but 

 rarely in Britain. (In Germany it is known as the Vhu, from its weird 

 peculiar cry, which has given rise to the legend of the " Wild Huntsman.") 

 It inhabits large forests. The plumage bears the closest resemblance to 

 the bark of old trees. The ears are surmounted by a tuft of erect 



