The Practical Value of Birds (Classic Reprint)

Excerpt from The Practical Value of Birds

Because of the fact that some species of insects and other pests which are normally kept within reasonable bounds, may, during especially favorable seasons or cycles of seasons increase so rapidly as to become very harmful, these birds which take a mixed diet are particularly valuable. Thus a bird species which ordinarily is largely vegetarian lives through seasons Of scarcity of insects, and then is ready to turn its attention to an insect diet whenever the insects become overabundant; whereas, if the birds were all exclusively insectivorous, comparatively few would survive seasons unfavorable to ih sects and thus be on hand to aid in the warfare against those pests when seasons favorable to insect life occur.

A species which is harmless, or even beneficial, in its natural habitat, may become injurious when transported to a new environment, where the natural checks upon its increase are wanting, or the lack of its natural food, or the presence Of a food which is more enjoyable, may cause a marked change in its food habits. It is said that the Skylark, green linnet and black thrush are considered beneficial in Europe, where they are native, but in New Zea land, into which country they have been introduced, they have developed traits which render them far from desirable additions to the fauna Of that It will be interesting to watch the effect of the introduction of the Little Gray Owl into New Zealand for the purpose of fighting the English sparrow Such importations are now, as a result of disastrous experience, prohibited by law in some countries, including the United States.

The introduction Of a species may disturb the balance as much as the extermination of one. European rats, accidentally introduced into Jamaica, became a great nuisance. The Indian mongoose was imported to destroy the rats. It turned its attention to game birds, poultry, young pigs and lambs, and became a great pest, also destroying many birds, snakes and lizards, which feed largely upon insects. This was followed by an increase of insect pests. Disaster also followed the introduction Of the mongoose into Hawaii, and its importation into the United States was barely prevented. Rabbits.

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