12 
paths. Comparatively small bodies of water deflect some species from 
their course, others unhesitatingly cross vast reaches of sea, indifferent to 
nearby and convenient land passages that are made use of by closely allied 
species. In some species the older birds precede; and in others the males 
precede the females. 
How birds find their way is still only vaguely understood, and indi- 
viduals far out of their natural range and course show clear evidence of 
being as hopelessly lost as any other animal would be on unfamiliar ground. 
Certainly experience has much to do with it and undoubtedly young birds 
are largely guided by the movements of their elders, who, presumably, 
through previous experience, already know and can lead the way. We can 
understand how birds can follow great landmarks — large river systems, 
mountain ranges, or seacoasts — in their journey, but no sense with which 
we are familiar explains how some species returns unerringly to lonely 
oceanic islands over wastes of monotonous sea. It may be that they have 
a special sense which aids them in orienting themselves. 
PROTECTION 
In food habits, birds are eminently adaptable: seeds, plants, fruit, 
insects, flesh, or fish are all acceptable to various species and, consequently, 
nearly all regions have their quota of appropriate birds. A bird lives fast, 
its heart beats more rapidly than that of other animals, the blood tempera- 
ture is higher, and it consumes an enormous amount of energy in flight. 
This feverish heat and strenuous exertion require a correspondingly large 
amount of food; consequently the bird as an economic factor is one to be 
regarded seriously. Though it may be an exaggeration to say, as some 
writers have implied, that the whole balance of nature depends upon birds 
and that without them the country would be a barren waste with no life 
other than insects, yet birds cannot be seriously reduced in number with- 
out the gravest results. The destruction of tons of weed seeds and millions 
of insects must necessarily have a great influence upon human welfare and 
neglect of this fact must seriously react upon any community that fails to 
give proper protection to its birds. 
However, the problem of the status of individual species of birds is not 
the simple thing that it superficially appears to be. More than a cursory 
examination is necessary and many things must be considered in order to 
arrive at the truth. Sometimes birds work in harmony with human welfare 
and sometimes against it. They may be directly beneficial at one season 
and harmful at another, or their indirect influence may alter the sum of 
their direct effects in a most surprising manner. 
General impressions then as to whether a bird is beneficial or harmful 
require careful checking. Mere casual observation in life is never sufficient 
to determine even its food supply. Modern practice bases such con- 
clusions almost entirely upon the examination of the stomach contents of 
wild birds taken throughout the year, which is the only evidence that is 
not subject to question. In this work the United States Biological Survey 
has examined and passed upon thousands of bird stomachs and the results 
of its researches are available to those who care to study and use them. 
As one of the factors in the delicate balance of nature, birds should be 
respected. 
