For indoor perches for pigeons individual perches shaped like an inverted V are most used. These are attached to the wall, one above another, about 12 or 14 inches apart. The pigeons rest on the upper edge of the perch, and the sloping sides prevent their plumage from being soiled by birds roosting above them. In the outdoor flies running boards are placed along the sides to make exercising and resting places for the birds, for they usually prefer a shelf of this kind to the ground. Long perches are also placed in the fly when the running boards do not give room for all the pigeons in the flock. Out of doors the birds get along very well on long perches, but in the house each wants a separate perch. Feed hoppers like those used for fowls are used in pigeon houses. Drinking vessels for pigeons should be of the fountain type, exposing only a small surface of water, because if the vessel is open the birds will bathe in it. For the bath any circular vessel with a depth of 4 or 5 inches and a diameter of 18 inches or over may be used. [Illustration: Fig. 211. Running boards in pigeon fly. (Photograph from Springer Brothers, Bridgeton, New Jersey)] =Ventilation and cleanliness.= The ventilation of a pigeon house is managed in the same way as that of a poultry house, by adjusting the openings in the front. Most kinds of pigeons are very rugged and, when fully feathered, can stand a great deal of cold. When a house is open in winter, some of the young, unfledged squabs may be chilled and die from exposure, but breeders agree that, on the whole, it is better to keep the windows or other openings for ventilation partly open at all times. While this causes some loss of the weaker squabs, it keeps the old birds in much better condition than when the house is tightly closed. [Illustration: Fig. 212. Constant water supply for pigeons] To keep the loft looking clean and neat the droppings should be removed from the floor, and from all shelves that can be cleaned without disturbing breeding birds, at least once a week. Many pigeon keepers clean the houses oftener than that, but if the ventilation is good and the droppings are dry and firm, a house may go uncleaned for weeks or months without detriment to the birds. It is customary to keep the floor of the pigeon loft thinly covered with fine gravel, coarse sand, sawdust, or chaff. To prevent the wind from the pigeons' wings from blowing this from the middle to the sides of the floor, a small box is placed in the middle of the floor. Whenever it is possible, the bath pan is placed outdoors, because in taking a bath pigeons splash the water a great deal, and if they are given the bath indoors, they will make a nasty mess of the house floor unless it is perfectly clean. The bath need not be given oftener than once or twice a week. In bad weather it is better to let them go without a bath than to have them take one and get chilled before their feathers dry.