Page:Popular Science Monthly Volume 55.djvu/845

Rh fully perform the duties of nidification, as all respectable feathered folk should. However, this parasitical habit breaks out, quite unexpectedly it must be conceded, in another American family of birds which is entirely distinct from the cuckoo group.

In America the cowbird, often called the cow bunting, is the only member of the avian household that spirits its eggs into the nests of other birds. The theory of evolution can do little toward accounting for the anomaly, and even if it should venture upon some suggestions it would still be just as difficult to explain the cause of the evolution in this special group, while all other avian groups follow the law of thrift and self-reliance.

The cowbird belongs to the family of birds scientifically known as Ideridæ, which includes such familiar species as the bobolinks, orioles, meadow larks, and the various kinds of blackbirds, none of which, I am glad to say, are parasites. The name Molothrus has been given to the genus that includes the cowbirds. They are confined to the American continent, having no analogues in the lands across the seas. The same may be said, indeed, of the whole Ideridæ family. It may be a matter of surprise to many persons that there are twelve species and subspecies of cowbirds in North and South America, for most of us are familiar only with the common cowbird (Molothrus ater) of our temperate regions. Of these twelve species only three are to be found within the limits of the United States, one is a resident of western Mexico and certain parts of Central America, while the rest find habitat exclusively in South America. A fresh field of investigation is open to some enterprising and ambitious naturalist who wishes to study several of these species, as comparatively little is known of their habits, and indeed much still remains to be learned of the whole genus, familiar as one or two of the species are. Their sly, surreptitious manners render them exceedingly difficult to study at close range and with anything like detail.

Are all of them parasites? It is probable they are—at least to a greater or less degree—except one, the bay-winged cowbird of South America, which I shall reserve for notice later on in this article. We might assert that our common cowbird is the parasite par excellence of the family, for, so far as I can learn from reading and observation, they never build their own nests or rear their own young, but shift all the duties of maternity, save the laying of the eggs, upon the shoulders of other innocent birds.

These avian "spongers" have a wide geographical range, inhabiting the greater part of the United States and southern Canada, except the extensive forest regions and some portions of the Southern States. The center of their abundance is the States bordering