300 ANIMAL INTELLIGENCE. 



southern United States ; and, as Mr. Wallace truly ob- 

 serves, 



Many facts have already been given which show that birds 

 do adapt their nests to the situations in which they place them ; 

 and the adoption of eaves, chimneys, and boxes by swallows, 

 wrens, and many other birds, shows that they are always ready 

 to take advantage of changed conditions. It is probable, there- 

 fore, that a permanent change of climate would cause many 

 birds to modify the form or materials of their abode, so as better 

 to protect their young. 1 



In America the change of habits in this respect under- 

 gone by the house-swallow has been accomplished within 

 the last three hundred years. 



Closely connected, if not identical, with this fact is 

 another, namely, that in some species which have been 

 watched closely for a sufficient length of time, a steady im- 

 provement in the construction of nests has been observed. 

 Thus C. G. Leroy, who filled the post of Ranger of Ver- 

 sailles about a century ago, and therefore had abundant 

 opportunities of studying the habits of animals, wrote an 

 essay on ' The Intelligence and Perfectibility of Animals 

 from a Philosophical Point of View.' In this essay he 

 has anticipated the American observer Wilson in noticing 

 that the nests of young birds are distinctly inferior to 

 those of older ones, both as regards their situation and 

 construction. As we have here independent testimony 

 of two good observers to a fact which in itself is not im- 

 probable, I think we may conclude that the nest-making 

 instinct admits of being supplemented, at any rate in 

 some birds, by the experience and intelligence of the 

 individual. M. Pouchet has also recorded that he has 

 found a decided improvement to have taken place in the 

 nests of the swallows at Rouen during his own lifetime ; 

 and this accords with the anticipation of Leroy that if our 

 observation extended over a sufficient length of time, and 

 in a manner sufficiently close, we should find that the ac- 

 cumulation of intelligent improvements by individuals of 

 successive generations would begin to tell upon the in- 



1 Natural Selection, pp. 232-3. 



