THE PHILOSOPHY OF BIRDS' XE87S. 229 



Our little gold-crested warbler also varies its nest 

 according to circumstances, building an open cup- 

 shaped nest where there is a natural canopy of thick 

 foliage, while in more exposed situations it forms a 

 perfect domed nest with a side entrance. Again, there 

 are decided imperfections in the nesting of many birds 

 which are quite compatible with our present theory, but 

 are hardly so with that of instinct, which is supposed 

 to be infallible. The Passenger pigeon of America 

 often crowds the branches with its nests till they break, 

 and the ground is strewn with shattered nests, eggs, 

 and young birds. Rooks' nests are often so imperfect 

 that during high winds the eggs fall out; but the 

 Window- Swallow is the most unfortunate in this re- 

 spect, for White, of Selborne, informs us that he has 

 seen them build, year after year, in places where their 

 nests are liable to be washed away by a heavy rain and 

 their young ones destroyed. 



Conclusion. 



A fair consideration of all these facts will, I think, 

 fully support the statement with which I commenced, 

 and show, that the mental faculties exhibited by birds in 

 the construction of their nests, are the same in kind as 

 those manifested by mankind in the formation of their 

 dwellings. These are, essentially, imitation, and a slow 

 and partial adaptation to new conditions. To compare 

 the work of birds with the highest manifestations of 

 human art and science, is totally beside the question. I 

 do not maintain that birds are gifted with reasoning 



