450 
ECONOMIC RELATIONS OF OUR BIRDS. 
It is only when forest-planting becomes a necessity that bud-eating birds, as 
such, can take the rank of enemies, unless, by any means, these birds should 
become very abundant. In any case, only the small bud-eaters, like the Purple 
Finch and some of the Linnets, whose small size render them valueless as food, 
and which, for this reason, would have to be controlled by the av^^arding of 
bounties or some similar means, need give us any apjDrehensions whatever. 
(2) A bird does us harm ivhen it preys upon shrews, moles and bats. These an¬ 
imals, owing to their insectivorous and nocturnal habits, and their, so far as 
known, inoffensive natures, are to be regarded as of great value. They are 
especially to be protected because they choose a time to feed when noxious in¬ 
sects are abroad in abundance and when their enemies are few. Birds, there¬ 
fore, which are extensively destructive to them, unless they have some very 
desirable traits, are to be regarded as enemies. 
Owls are the principal birds known to feed upon these animals. 
(3) A bird is harmftd to us when it preys upoji other beneficial birds and their 
eggs. A species which makes a practice of preying upon birds’ eggs or their 
young, or which has the ability and disposition to capture mature birds, must 
certainly do a very important work for us in compensation to be encouraged in 
agricultural districts, at least until after experience has proved that its services 
are needed to prevent an undue increase of certain birds. All of our Hawks, 
Owls, Shrikes and Crows are known to be, or may be suspected of being, more 
or less destructive to birds in one or more of their stages of development, but to 
what extent, observations, so far as they have been published, are too limited and 
indefinite to allow any very definite conclusions to be drawn. 
(4) A bird is harmful when it feeds upon lizards and'perhaps our smallest 
species of snakes. As the food of these animals probably consists almost entirely 
of insects, they are to be regarded as beneficial, until shown to be detrimental. 
(5) A bird is harmful when it feeds upon frogs, toads and salamanders. Enough 
has already been said in regard to frogs and toads to show what their economic 
relations are, and how birds must be regarded which feed extensively upon 
them. Salamanders probably occupy a similar, though less important position. 
(6) A bird is detrimental when it feeds upon the parasites of noxious animals, 
and especially upon those of noxious insects. Parasites are regarded as the most 
potent agents which serve to keep noxious insects within safe bounds, and that 
their influence is very great, there can be no doubt. This, however, is to be said 
in regard to them: Many, api^areutly, only become extremely abundant when 
the insects upon which they prey have assumed such numbers as often to 
commit wide-spread ravages. Their influence has a tendency toward spasmodic 
rather than steady action. They are, as it were, the last reserves which Nature 
holds back for those emergencies when favorable conditions of climate shall let 
loose upon the world such an abundance of insects as cannot be controlled by 
other means. 
The'fateful army-worm, whose history is so well given by Riley, i illustrates 
well what is meant. In spite of the combined action of its nine known para¬ 
sites, this worm, at irregular intervals, marches its gigantic armies over fields 
of grass and grain, for a season, and then disappears. 
Again, parasites do not stop the ravages of an insect at once as birds do. The 
larvae which they infest are allowed to pass through the destructive period of 
their lives, apparently with appetites unimpaired. They save future rather than 
present crops, while birds do both. 
1 Second Annual Report, p. 37. 
