WAYS OF NATURE 



of paper, and dry grass. After the third day the site 

 on the branch was bare, the wind having swept 

 away every vestige of the nest. As I passed beneath 

 the tree I saw the thrush standing where the nest 

 had been, apparently in deep thought. A few days 

 afterward I looked again, and the nest was com- 

 pleted. The bird had got ahead of the wind at 

 last. The nesting-instinct had triumphed over the 

 weather. 



Take the case of the little yellow warbler when 

 the cowbird drops her egg into its nest — does any- 

 thing like a process of thought or reflection pass in 

 the bird's mind then ? The warbler is much dis- 

 turbed when she discovers the strange egg, and her 

 mate appears to share her agitation. Then after a 

 time, and after the two have apparently considered 

 the matter together, the mother bird proceeds to 

 bury the egg by building another nest on top of the 

 old one. If another cowbird's egg is dropped in this 

 one, she will proceed to get rid of this in the same 

 way. This all looks very like reflection. But let us 

 consider the matter a moment. This thing between 

 the cowbird and the warbler has been going on for 

 innumerable generations. The yellow warbler 

 seems to be the favorite host of this parasite, and 

 something like a special instinct may have grown up 

 in the warbler with reference to this strange egg. 

 The bird reacts, as the psychologists say, at sight of 

 it, then she proceeds to dispose of it in the way 

 156 



