. THE PHILOSOPHY OF BIRDS’ NESTS, 227 
gone before us? We have not even been able to 
discover or develope 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 character- 
istic form of nest, exactly adapted to their wants and 
habits. 
Birds do Alter and Improve their Nests when altered. 
Conditions require it. 
The great uniformity in the architecture of each 
species of bird which has been supposed to prove a 
nest-building instinct, we may, therefore, fairly im- 
pute to the uniformity of the conditions under which 
each species lives. Their range is often very 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 advan- 
tage 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 affec- 
tion for the church steeple which can hardly be ex- 
plained 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, 
