2234 THE PHILOSOPHY OF BIRDS NESTS. 
search for food, and it seems highly probable that the 
older birds would begin building first, and that those 
born the preceding summer would follow their ex- 
ample, learning from them how the foundations of the 
nest are laid and the materials put together.* 
Again, we have no right to assume that young 
birds generally pair together. It seems probable 
that in each pair there is most frequently only one 
bird born the preceding summer, who would be 
guided, to some extent, by its partner. 
My friend, Mr. Richard Spruce, the well-known 
traveller and botanist, thinks this is the case, and 
has kindly allowed me to publish the following 
observations, which he sent me after reading my book. 
How young Birds may learn to build Nests. 
* Among the Indians of Peru and Ecuador, many of 
whose customs are relics of the semi-civilisation that 
prevailed before the Spanish conquest, it is usual for 
the young men to marry old women, and the young 
women old men. A young man, they say, accus- 
tomed to be tended by his mother, would fare ill if 
* It has been very pertinently remarked by a friend, that, 
if young birds did observe the nest they were reared in, they 
would consider it to be a natural production like the leaves 
and branches and matted twigs that surrounded it, and could 
not possibly conclude that their parents had constructed the 
one and not the other. This may be a valid objection, and, if 
so, we shall have to depend on the mode of instruction de- 
scribed in the succeeding paragraphs, but the question can 
only be finally decided by a careful set of experiments. 
