DO ANIMALS THINK AND REFLECT? 



above described. All yellow warblers act in the same 

 manner, which is the way of instinct. Now if this 

 procedure was the result of an individual thought 

 or calculation on the part of the birds, they would 

 not all do the same thing ; different lines of conduct 

 would be hit upon. How much simpler and easier 

 it would be to throw the egg out — how much more 

 like an act of rational intelligence. So far as I know, 

 no bird does eject this parasitical egg, and no other 

 bird besides the yellow warbler gets rid of it in 

 the way I have described. I have found a deserted 

 phoebe's nest with one egg of the phcebe and one of 

 the cowbird in it. 



Some of our wild birds have changed their habits 

 of nesting, coming from the woods and the rocks to 

 the protection of our buildings. The phoebe-bird 

 and the cliff swallow are marked examples. We 

 ascribe the change to the birds' intelligence, but to 

 my mind it shows only their natural adaptiveness. 

 Take the cliff swallow, for instance; it has largely 

 left the cliffs for the eaves of our buildings. How nat- 

 urally and instinctively this change has come about! 

 In an open farming country insect life is much more 

 varied and abundant than in a wild, unsettled coun- 

 try. This greater food supply naturally attracts the 

 swallows. Then the protecting eaves of the buildings 

 would stimulate their nesting-instincts. The abun- 

 dance of mud along the highways and about the 

 farm would also no doubt have its effect, and the 

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