228 THE PHILOSOPHY OF BIRDS’ NESTS. 
instead of the single hairs and vegetable fibres it has 
painfully to seek in wilder regions; and Wilson, a 
most careful observer, believes that it improves in 
nest-building by practice—the older birds making 
the best nests. The purple martin takes possession 
of empty gourds or small boxes, stuck up for its re- 
ception in almost every village and farm in America; 
and several of the American wrens will also build 
in cigar boxes, with a small hole cut in them, if 
placed in a suitable situation. The orchard oriole of 
the United States offers us an excellent example of 
a bird which modifies its nest according to circum- 
stances. When built among firm and stiff branches 
the nest is very shallow, but if, as is often the 
case, it is suspended from the slender twigs of the 
weeping willow, it is made much deeper, so that when 
swayed about violently by the wind the young may 
not tumble out. It has been observed also, that the 
nests built in the warm Southern States are much 
slighter and more porous in texture than those in the 
colder regions of the north. Our own house-sparrow 
equally well adapts himself to circumstances. When 
he builds in trees, as he, no doubt, always did origin- 
ally, he constructs a well-made domed nest, perfectly 
fitted to protect his young ones; but when he can 
find a convenient hole in a building or among thatch, 
or in any well-sheltered place, he takes much less 
trouble, and forms a very loosely-built nest. 
A curious example of a recent change of habits has 
occurred in Jamaica, Previous to 1854, the palm 
