56 'Journal of Comparative Neurology and Psychology. 



leave the young uncovered part of the time ; at first they leave them 

 uncovered only when they themselves come off to feed, then leaving 

 them for a greater and greater part of the day till finally they cease 

 to cover them at all. This last occurs on the tenth or eleventh or 

 twelfth day. It is not surprising that the parent leaves the nest at 

 tills time, for the young hird has grown so large that the parent 

 ciinnot qwiUi cover it, not to speak of covering two such big young- 

 sters. When there, are two young in the nest, the parents leave 

 sooner, I think, than when there happens to he only one. The nest- 

 lings have been as rapid in development as they have been in growth. 

 The feathers on the wings and back have grown sufficiently to hide 

 the skin. The eyes are wide open, and the birds are looking about 

 most of the time; tliey are more active altogether, their activity being 

 evidently in preparation for activity after leaving flu; nest. For 

 days before venturing from the nest the young may stand and stretch 

 themselves in the fasliion of the adult, first i-aising both wings above 

 tlic back, and tlicti stretching each wing in tnr-n together with the 

 corresponding legs. The day before leaving, too, J have seen a yotmg 

 one stand in the nest and flap its wings as if practicing for flight. 



The expression of fear has at this time reached a maximum. If 

 a hand be brought near, the young bird scpiats down in the hollow 

 of the nest, making itself remarkably fhit, erects all the feathers, 

 draws its head down while at the same time pointing its bill toward 

 the intniding lunid, and repeatedly shuls tlic bill with a sounding 

 snap. The flatlciiiiig of ihc 1)ody is very characteristic of the nest- 

 ling, for it is absent, in its typical form, in adults, beginning to de- 

 cline just before the young leaves the nest. The expression of fear 

 thus reaches a maximum development bfd'ore any other, indeed it 

 gradually disappears, to a great extent, as the young becomes older; 

 the snap of the bill, especially, beccnnes weaker after the l)ird has 

 learned to fly, and degenerates in the adult into that rudiment of a 

 snap which, though it can be seen, can hardly be heard. The age at 

 which the young bird learns to fly is, ])retty definitely, the age at 

 wiiich it gives up the expression of fear. When able to fly, the bird 

 shows a'arm instead of fear, in the presence of dangerous objects; 

 it is imjielled to flee rather than to remain and make a show of resist- 



