The vireos form a peculiar and interesting family — the Vireonidae, which includes about fifty species. All are strictly American and the larger number inhabit only the forest or shrubby regions of Central and South America. The name vireo signifies a green finch and is from the Latin word meaning "to be green." The body color of nearly all the species is more or less olive green.

About fifteen species frequent the United States. These are all members of the genus Vireo, and some of them have a wide range, only equaled in extent by some of the warblers.

Dr. Coues has said of these birds: "Next after the warblers the greenlets (vireos) are the most delightful of our forest birds, though their charms address the ear and not the eve. Clad in simple tints that harmonize with the verdure, these gentle songsters warble their lays unseen, while the foliage itself seems stirred to music. In the quaint and curious ditty of the white-eye, in the earnest, voluble strains of the red-eye, in the tender secret that the warbling vireo confides in whispers to the passing breeze, he is insensible who does not hear the echo of thoughts he never clothes in words."

The vireos are strikingly alike. In habit, in color, in structure, in size and in their home-building peculiarities they resemble each other. Their eggs are similar and "fashioned almost as from the same mold, and colored as if by the same brush."

The vireos build pensile nests that reingeniously concealed under the surrounding foliage. They are in the form of a rather deep cut, which is suspended from two or more converging twigs. The materials used in the construction are similar in all cases, though they vary somewhat according to the locality and the abundance of desirable textiles. A favorite substance used by some of the birds is the tough and flexible fibers of the inner hark of trees. Thoreau, speaking of this habit, says: "What a wonderful genius it is that leads the vireo to select the tough fiber of the inner bark instead of the more brittle, grasses!"

The White-eyed Vireo has an extensive range, extending over the eastern United States from the Atlantic Ocean to the great plains and from Mexico and Guatemala, where it winters, northward to the borders of British America. It nests practically throughout its range within the United States.