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 wrnuld 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. Gr. Leroy, who filled Lhe post of Eanger of Ver- 
sailles about a century ago, and therefore had abundant 
opportunities of studying the habits of animals, wrote an 
essay on 6 The Intelligence and Perfectibility of Animals 
from a Philosophical Point of View. 5 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 m- 
1 Natural Selection , pp. 232-3, 
