io6 Instinct, 



can furnish, — let him work a month, and if he can 

 produce as good a nest as the bird will build in a 

 week with its beak and claws, we will listen patient- 

 ly to the arguments to prove that birds learn by 

 observation to build nests. We can hardly do so 

 now. 



But it is said that some nests of the same spe- 

 cies are better built than others. Certainly. 

 Sometimes undoubtedly it is impossible for the 

 bird to find the best materials; sometimes there 

 may be structural difficulties in the bird that inter- 

 fere with skilful work, and it would certainly be dif- 

 ferent from any thing else in nature if we did not 

 find birds of the same species differing somewhat in 

 the nest-building power, as they do in size, beauty 

 of plumage and power of song. It is possible that 

 there is real improvement by practice, as Wilson 

 long ago suggested, but there are no facts that are 

 conclusive proof of it. And after discounting all 

 differences found among nests of the same species, 

 we have still remaining in the manufacture of some 

 nests, manifestations of skill that no human work- 

 man can approach with the same materials. A 

 careful examination of the nests of birds will con- 

 vince any one that there is given to each species, 

 without experience or instruction, a tendency to 

 build nests, that arises as spontaneously as hunger 

 arises at stated times from waste of tissue. There is 

 also an impulse to select certain materials for the dif- 

 ferent parts of the nest ; and this impulse is as fixed 

 as is the law of growth which gives to the bird a 

 certain color or thickness of feather, both of which 



