416 



THE BIRDS 



meditation, must be wise. However, when night comes the owls no 

 longer sit, but become quite active as they fly about in search of nocturnal 

 rodents. They have eyes that are probably the keenest in the animal 

 kingdom. During the daytime the pupils become reduced to small 

 dots, but, contrary to superstition, they can see during the daytime. At 

 night, in the reduced light, the pupils enlarge tremendously, enabling 



Courtesy Chicago Natural History Museum 



Fig. 27.7. The bald eagle, our national bird, is a symbol of freedom as it soars unre- 

 strained high in the air. 



them to see clearly in the darkest forests. The pupils are able to change 

 their size almost instantly to accommodate for changing light intensity, 

 so that an owl can chase a mouse from the bright moonlight into a dark 

 forest without difficulty. This can easily be demonstrated ; if a flash- 

 light is passed back and forth in front of an owl's eyes the pupils contract 

 and dilate as rapidly as the light passes across in front of them. We 

 can realize how superior this is to our own pupil accommodation when 

 we remember how we stumble around and sometimes sit in someone's lap 



