112 NATURAL SELECTION v 



when fabricating their nest. They had no standard to work 

 by, no nests of their own kind to copy, no older birds to give 

 them any instruction, and the result is the abnormal structure 

 I have just described. Perhaps these chaffinches imitated in 

 some degree the nest of some New Zealand species ; or it 

 may be that the few resemblances to the typical nest of the 

 Palsearctic chaffinch are the results of memory the dim 

 remembrance of the nest in which they had been reared, but 

 which had almost been effaced by novel surroundings and 

 changed conditions of life. Any way we have here, at least, 

 a most interesting and convincing proof that birds do not 

 make their nests by blind instinct, but by imitating the nest 

 in which they were reared, aided largely by rudimentary 

 reason and by memory." l 



This experiment also leaves much to be desired, but it 

 undoubtedly shows that instinct alone does not determine 

 the form and structure of a bird's nest, or we should not see 

 so great a departure from the type in the case of the New 

 Zealand chaffinches. 



The Skill exhibited in Nest-building Exaggerated 



We are too apt to assume that because a nest appears to 

 us delicately and artfully built, it therefore requires much 

 special knowledge and acquired skill (or their substitute, 

 instinct) in the bird who builds it. We forget that it is 

 formed twig by twig and fibre by fibre, rudely enough at first, 

 but crevices and irregularities, which must seem huge gaps 

 and chasms in tiie eyes of the little builders, are filled up by 

 twigs and stalks pushed in by slender beak and active foot, 

 and that the wool, feathers, or horsehair are laid thread by 

 thread, so that the result seems a marvel of ingenuity to us, 

 just as would the rudest Indian hut to a native of Brobdignag. 



Levaillant has given an account of the process of nest- 

 building by a little African warbler, which sufficiently shows 

 that a very beautiful structure may be produced with very 

 little art. The foundation was laid of moss and flax inter- 

 woven with grass and tufts of cotton, and presented a rude 

 mass, five or six inches in diameter, and four inches thick. 

 This was pressed and trampled down repeatedly, so as at last 

 1 Nature, voL xxxi. p. 533 (April 1885). 



