Our Northern Shrike, or Butcherbird, feeds chiefly on small birds and mice, while the southern species, or Loggerhead, is a great destroyer of grasshoppers and he also eats lizards and small snakes.
The Vireos, (Family _Vireonidæ_) number fifty species, all American. They search the foliage carefully for leaf-eating insects and their eggs, and examine the crevices in the bark for eggs of the injurious wood-boring insects. They are therefore unusually beneficial birds.
Bearing a general resemblance in size and color to many of the Warblers, Vireos are sometimes confused with members of that family. They are, however, as a rule, more deliberate in their motions and not such active flutterers as are many of the Warblers. They are also more musical, all the Vireos having characteristic songs, which if not always highly musical, are generally noticeable, pronounced and unmistakable.
The nests of all our Vireos are pendant, deeply cup-shaped structures usually hung between the forks of a crotch, to the arms of which they are most skilfully woven.
The Warblers, (Family _Mniotiltidæ_) like the Vireos are distinctly American birds, indeed they may be called characteristic North American birds since most of the one hundred odd species are found north of Mexico. Between thirty and forty species of these active, beautiful little creatures may be found in the course of a year at a single locality in the Eastern States and they therefore constitute an exceedingly important element in our bird-life. Most of them come in May at the height of the spring migration; when the woods often swarm with them as they flit from limb to limb in pursuit of their insect food. The larger number of them pass onward to their northern homes and in September they return to us in increased numbers.
The beauty of their plumage, the briefness but regularity of their visits, the rarity of certain species, combine to make the Warblers especially attractive to the field student and their charms are heightened by the difficulty with which many of them are identified. Study them as we may there are still species which have escaped us.
By far the larger number of Warblers may be described as flutterers that feed agilely about the terminal branches, (genera _Dendroica_ and _Helminthophila_); others are true flycatchers, so far as feeding habit is concerned, (genera _Setophaga_ and _Wilsonia_,) while others still feed in the undergrowth or on the ground, (genera _Geothlypis_ and _Seiurus_). Insects constitute almost their entire fare and they are among our most beneficial birds.