INTRODUCTORY 



seen and appreciated by the human observer 

 alone. 



But if birds display no taste for the beautiful in 

 their nests, their Intelligence in constructing them 

 is beyond the slightest question. This intelligence — 

 or perhaps reason is a better term — is abundantly 

 manifest from the selection of the site up to the 

 moment the last scrap of material is worked into the 

 structure. In dealing with this part of the subject 

 we reach a point in which it becomes necessary to 

 decide whether a bird builds its nest by the guidance 

 of blind instinct or by the exercise of its mental 

 powers. On the one hand there are not a few able 

 naturalists who believe that a bird builds by instinct ; 

 that a young bird is born with the power to make a 

 nest typical of its species when the time comes for it 

 to exert its inherited power in this direction. This 

 opinion, we need scarcely say, is almost universally 

 shared by the popular lover of birds, although very 

 little thought, reasoning or experiment would be 

 required to show that it is as untenable as it is 

 unreasonable. On the other hand, a small but in- 

 creasing number of naturalists, at the head of which 

 we must in fairness place Alfred Russel Wallace, have 

 sought to show that the nest-building capabilities of 

 birds may be satisfactorily explained by the exertion 

 of a reasoning faculty. 



Now Instinct, which we may define as Inherited 

 Habit, in a young bird is by no means sufficient to 



