94 Wild Birds and their Haunts 



With respect to owls, as well as night-prowling animals, 

 the eye is unquestionably very sensitive. 



Of the barred owl an experienced naturalist remarks, 

 ' ' Its power of sight during the day seems to be rather of 

 an equivocal character, as I once saw one alight on the 

 back of a cow, which it left so suddenly afterwards, when 

 the cow moved, as to prove to me that it had mistaken the 

 object on which it had perched for something else. At 

 otner times I have observed that the approach of the grey 

 squirrel intimidated them, if one of these animals acci- 

 dentally jumped on a branch close to them, although the 

 owl destroys a number of them during twilight." 



Wilson says of the snowy owl that ' ' the conformation 

 of the eye forms a curious and interesting subject to the 

 young anatomist. The globe of the eye is immoveably 

 fixed in its socket by a strong, elastic, hard, cartilaginous 

 case, in the form of a truncated cone. This case, being 

 closely covered with a skin, appears at first to be of one 

 continued piece, but on removing the exterior membrane 

 it is found to be formed of no less than fifteen pieces, 

 placed like the staves of a cask, overlapping a little at the 

 base or narrow end, and seem as if capable of being en- 

 larged or contracted, perhaps by the muscular membrane 

 in which they are encased." 



In nocturnal birds — it has been remarked by several 

 writers — the eye, besides being comparatively very large, 

 is flat (comprime) both before and behind, while the trans- 

 parent cornea is placed at the end of a sort of tube formed 

 by the bony portion of the sclerotic. The retina is conse- 

 quently comparatively very large and extended, and the 

 iris also ; while the membranes, being probably more soft 

 and delicate, are more susceptible of impressions from a 

 small quantity of light. The nictitating membrane is 

 also very large, and the upper eyelid, unlike other birds', 

 is moveable. 



I have adverted to the method of catching larks by 

 means of a looking-glass, ieferring to the remarkable 

 curiosity of birds as the probable cause of their being 

 attracted to the bright glass. Whether it is on a similar 

 principle that ravens, jays, and magpies (corvidce), are 



