put forth all his energy in his
vocal efforts; and if, while singing, he should start on a run even on
level ground, he Would become exhausted at once.... The average person
uses only about one seventh of his lung capacity in ordinary breathing,
the rest of the air remaining at the bottom of the lung, being termed
'residual.' As this is vitiated by its stay in the lung, it does harm
rather than good by its presence.... As we have seen, the lungs of a
bird are small and non-elastic, but this is more than compensated by the
continuous passage of fresh air, passing not only into but entirely
_through_ the lungs into the air-sacs, giving, therefore, the very best
chance for oxygenation to take place in every portion of the lungs. When
we compare the estimated number of breaths which birds and men take in a
minute,--thirteen to sixteen in the latter, twenty to sixty in
birds,--we realize better how birds can perform such wonderful feats of
song and flight."

A BOOK LIST

For getting acquainted with birds, we no more need books than we need
books for getting acquainted with people. One bird, if rightly
known,--as with one person understood,--will teach us more than we can
learn by reading. But since no one has time to learn for himself more
than a few things about many birds, or many things about a few birds, it
is pleasant and companionable and helpful to have even a second-hand
share in what other people have learned. For myself, I like to watch
both the bird in the bush through my own eyes and the bird in the book
through the eyes of some other observer. So it seems but fair to share
the names of books that have interested me in one way or another during
the preparation of my own. If it seems to anyone a short list, I can but
say that I do not know all the good books about birds, and therefore
many (and perhaps some of the best) have been omitted. If it seems to
anyone a long list, I would suggest that, if it contains more than you
may find in your public library, or more than you care to put on your
own shelves, or more than can be secured for the school library, the
list may be helpful for selection--perhaps some of them will be where
you can find and use them. Certain of them, as their titles indicate,
are devoted exclusively to birds; and others include other outdoor
things as well--as happens many a time when we start out on a bird-quest
of our own, and find other treasures, too, in plenty.

If I could hav