There are a number of birds which are valuable friends to all the people because they are scavengers. The Herring Gull, which is the commonest gull of the harbors of the United States, and which is also found on inland lakes and rivers, by feeding upon all kinds of refuse animal and plant materials makes the waters about our cities more healthful. This is especially true of the coast cities which dump their garbage into the waters not far distant. The Turkey Vulture, the Black Vulture or Carrion-Crow, and the California Condor make the fields and woods of the country more healthful by devouring the carcasses of animals, and the first two species eat the offal from slaughter houses and even scraps of meat from the markets in some of our Southern cities. [Illustration: COMMON TERN A close relative of the gulls. Range: Northern Hemisphere, northern South America and Africa.] [Illustration: GREAT BLUE HERON Frequently miscalled Blue "Crane." The long legs indicate that this is a wading bird. Range: Western Hemisphere.] The most valuable group of birds from the standpoint of the farmers, the orchardists, and the gardeners is the insect-eating birds. Among these are the Wood Pewee, the Phoebe, the Kingbird, and all of the Flycatchers; the Purple Martin and all of the Swallows; the Nighthawk and Whip-poor-will. The Yellow-billed and Black-billed Cuckoos and the Baltimore Oriole feed largely upon tent caterpillars and others caterpillars which defoliate the fruit and shade trees. The Sparrow Hawk has been wrongly named, for it eats a thousand times as many grasshoppers as it does sparrows. The Chickadees, Brown Creepers, and many of the Warblers feed largely upon insects and insect eggs which they glean chiefly from the trees. The Rose-breasted Grosbeak and the Bob-White eat the Colorado potato-beetle. In the West the Franklin's Gull follows the farmer in the fields and picks up great numbers of destructive insects. In learning the value of our feathered friends it is necessary to learn to know the birds, and in this quest great help can be obtained from books. Beginners will find the following useful: "Land Birds East of the Rockies," by Chester A. Reed. "Water and Game Birds," by Chester A. Reed. "Western Bird Guide," by Chester A. Reed. (All published by Doubleday, Page & Co.) For more advanced students the following are recommended: "Handbook of Birds of Eastern North America," by Frank M. Chapman (D. Appleton & Co.). "Handbook of Birds of Eastern North America," by Florence Merriam Bailey (Houghton, Mifflin & Co.). Our study of birds should not stop with the name, because we shall find many things of interest in the home life of birds, many things that seem to reflect our own lives. (See "Home Life of Wild Birds," by F. H. Herrick. G. P. Putnam's Sons.)