340 NATURAL HISTORY OF BIRDS. 



to suppose their vision is much restricted in the daytime, notwithstanding they belong 

 to a group of owls commonly regarded as nocturnal. They passed most of the day, 

 indeed, crouching in the shadow of the tent, and it was only toward sundown that 

 they became active, flying the length of their tether in the attempt to reach the 

 ridge of the tent ; yet their vision was acute at all hours. I often saw them look up 

 and follow with their eyes the motions of a grasshopper or butterfly flickering several 

 yards up in the air. On one occasion in particular, I saw them both gazing stead- 

 fastly, and on looking up to see what had attracted their attention, I was myself 

 blinded by the glare, for the direction was exactly in the sun's eye. But a few 

 moments afterwards I discovered a pair of white cranes floating in circles half a mile 

 high. The owl's eyes endured a glare that my own could not, and the birds certainly 

 saw the objects, for they slowly moved the head as the cranes passed over. The best 

 of the supposed performances of an eagle soaring in the sun's eye could not excel 

 this. Nor was the inner eyelid drawn over the ball to shade it. I had abundant 

 evidence, on this and numerous other occasions, that the movements of the birds' iris 

 are entirely under the control of the will, instead, as commonly supposed, of being 

 automatic, depending upon the stimulus of light. I frequently saw them instantane- 

 ously relax or contract the quivering iris in accommodating their vision to different 

 objects or different distances ; and, moreover, they could move the hides indepen- 

 dently of each other; for they often looked at objects with one eye only, the other 

 being sleepily half closed ; and on such occasions the pupils were generally of different 

 sizes. They varied in diameter from that of a small split-pea, to that of a finger- 

 ring ; in the latter condition the iris was a mere margin about a tenth of an inch in 

 diameter. In the night-time I always found the pupil largely, if not fully, dilated ; at 

 every stage of contraction it remained perfectly circular." 



Others have been less successful in taming these birds, some failing entirely, 

 others making but a partial success. In the " Auk," Mr. J. W. Banks has given some 

 of his experience in this respect, together with many interesting notes, from which we 

 select the following : " Nothing in the shape of fresh fish or flesh is neglected by the 

 owl when hungry, though her choice is for wild birds, and she will take small animals 

 in preference to beef or mutton. A rat or squirrel is always swallowed whole, and 

 about every second or third day the fur and bones are ejected, rolled into a hard 

 pellet as large as a grouse's egg. Just before ejecting these pellets the bird's appear- 

 ance is very distressing. The first time I observed it I thought she must be ill, but as 

 soon as the pellet is out she immediately recovers. The ' hoot ' is made with the bill 

 firmly closed ; the air is forced into the mouth and upper part of the throat, the latter 

 being puffed out to the size of a large orange." 



The breeding habits of the great horned-owl vary widely in different parts of the 

 country. Audubon's experience led him to believe that it nested usually in hollow 

 trees, but in two cases he knew it to nest in the clefts of rocks. In many parts of 

 the United States it builds a large, open nest, toward the top of a tall tree; this 

 seems to be usually the case in New England, where the eggs are ordinai-ily but two 

 (rarely three and never more) and are laid between the middle of February and the 

 middle of March. 



At that early date there is often scarcely a sign of spring and the eggs must need 

 constant care to prevent freezing. The late Mr. W. W. Coe, of Portland, Conn., who 

 took one or more sets of this bird's eggs every season for many years, informed us that 

 one morning, after a heavy fall of snow, he saw in the top of a tree, while trying to 



