Another large class of birds,--the marsh-hawk, Harris hawk, red-tailed hawk, red-shouldered hawk, short-tailed hawk, white-tailed hawk, Swainson hawk, short-winged hawk, broad-winged hawk, Mexican black hawk, Mexican goshawk, sparrow-hawk, barn-owl, long-eared owl, short-eared owl, great gray owl, barred owl, western owl, Richardson owl, screech-owl, snowy owl, hawk-owl, burrowing owl, pigmy owl and elf owl--live mostly on destructive mammals, insects, frogs and snakes, but they eat some birds and some of them occasionally catch poultry. Young ones do much more harm than the full-grown ones, probably because they find poultry and birds easier to obtain than other food. These species all do great good on the farm and in the orchard and if their natural food is plentiful and the number of the birds of prey limited, they should be allowed to remain, even though they occasionally do harm; but they can not be allowed to increase greatly in a region without becoming a nuisance. In another class the golden and bald eagles, pigeon and Richardson hawks, prairie falcon and great horned owl do considerable harm, and the good and bad qualities about balance. In a poorly settled region, where there is plenty of natural food, a few of these birds will bring forth little complaint, but in a section where there are few ground-squirrels, prairie-dogs, gophers, rabbits and woodchucks, where poultry is raised extensively, and useful birds are numerous they will do great harm and farmers will usually want to keep them down entirely. The gyrfalcons, duck-hawks, sharp-shinned hawk, Cooper hawk and goshawk live almost entirely on food that is desired by man,--poultry, game birds and many varieties of our best insect-destroying birds, and they eat almost nothing that is harmful to man. The numbers of these birds should be reduced as much as possible: but in general it may be said that the birds of prey--the hawks and owls--are among the most, if not the most, valuable birds that are engaged in helping the farmer by destroying the natural enemies of agriculture. Among the smaller birds which do much good, but of which complaints are made because they eat some fruit and grain are the woodpeckers, including the flickers, cedar-birds, robins, cat-birds, thrashers, crows and blackbirds. The woodpeckers are the great natural protection of the forests by waging constant warfare on the wood-boring insects and ants beneath the bark where no other birds can reach them. They are equally useful in an orchard except that here man may only at great trouble and expense partly hold them in check. Downy woodpeckers are also great eaters of scales, and the fruit grower need not begrudge the red-headed woodpecker a meal of cherries or apples, especially as it will usually be found that it is the wormy fruit that is attacked. The flicker or gold-winged woodpecker lives largely on ants, of which he eats immense quantities, seeking them not only in the trees but on the ground.