114 NATURAL SELECTION v 
architecture, however exquisitely beautiful, is false in prin- 
ciple, and is by no means a good example of the application 
of reason to the art of building. And what do most of us 
do at the present day but imitate the buildings of those that 
have gone before us? We have not even been able to dis- 
cover or develop any definite style of building best suited for 
us. We have no characteristic national style of architecture, 
and to that extent are even below the birds, who have each 
their characteristic form of nest, exactly adapted to their 
wants and habits. 
Birds do Alter and Improve their Nests when altered Con- 
ditions require it 
The great uniformity in the architecture of each species of 
bird which has been supposed to prove a nest-building instinct, 
may, therefore, fairly be imputed to the uniformity of the 
conditions under which each species lives. Their range is 
often limited, and they very seldom permanently change 
their country, so as to be placed in new conditions. When, 
however, new conditions do occur, they take advantage of 
them just as freely and wisely as man could do. The 
chimney and house-swallows are a standing proof of a 
change of habit since chimneys and houses were built, and 
in America this change has taken place within about three 
hundred years. Thread and worsted are now used in many 
nests instead of wool and horsehair, and the jackdaw shows 
an affection for the church steeple, which can hardly be 
explained by instinct. In the more thickly populated parts 
of the United States the Baltimore Oriole uses all sorts of 
pieces of string, skeins of silk, or the gardener’s bass, to weave 
into its fine pensile nest, instead of the single hairs and vege- 
table fibres it has painfully to seek in wilder regions; and, 
as already stated, Wilson, a most careful observer, believes 
that it improves in nest-building by practice—the older birds 
making the best nests. More recently, Dr. Abbott, the well- 
known American naturalist, has studied the nests of the 
Baltimore Oriole. He found that, away from the habitations 
of man, the orioles built concealing nests; but in villages 
and cities, on the other hand, where they were in no special 
danger from predatory hawks (or more probably from snakes) 
