SIGHT OF OWLS IN DAYTIME 229 



under water than we do ; at any rate it is interesting 

 to note that just as we use a water-glass to examine 

 the bottom, so do Grebes and Cormorants often 

 put their head under water to beyond the eyes 

 before diving to get a clear view. These hunters 

 under water can, however, generally see as well in 

 the air as any ordinary birds ; in fact, those I have 

 mentioned, and such diving-ducks as Golden-eye 

 and Mergansers, are notoriously very wary and 

 alert birds. Penguins, however, are suspected of 

 being short-sighted when out of water. 



The powers of night vision which Owls and 

 ^Nightjars possess, also, do not seem to interfere 

 with their vision by day, the idea that they are 

 dazzled by daylight being solely due to the fact 

 that they are unwilling to move in the day. When 

 they are actually on the wing, they fly well enough 

 and avoid dangers and obstacles quite successfully, 

 and in captivity they show interest in birds flying 

 over, and even bask in the sun. In the case of 

 Owls, the curious peering movements of the head 

 certainly give the idea of bad sight, but these 

 gestures are indulged in just as much in the dusk 

 of the evening as in daylight, being merely a trick 

 of habit ; indeed, something similar is seen in the 

 more jerky head-movements of the Hawks. 



The blinking of the upper eyelid in Owls is also 

 a very human action which may have helped to 

 suggest the idea of blindness in daylight, almost 

 all other birds wiriing with the inner or third 

 eyelid, which is drawn so rapidly across the eye 



