If the snow lies long on the ground, so that the fowls are confined to the house much of the time in winter, the allowance of floor space should be about 5 sq. ft. per bird. Where the snow rarely lies more than a day or two at a time, less space may be given, because the birds will not occupy the house much of the time during the day. Under such conditions the allowance of floor space may be as low as 3 sq. ft. per bird. Those who go to this limit, however, should consider that, in the unusual case of a snowstorm keeping the hens confined to the house for more than a very few days, overcrowding may cause losses that more than offset what was gained by using the highest capacity of the house. Usually a flock of fifty hens needs a house with a floor surface of about 250 sq. ft. This is obtained in a house 16 ft. square or in a house 12 ft. × 24 ft. A house 20 ft. square is about right for seventy-five or eighty hens, and is not badly overcrowded if one hundred medium-sized birds are put into it. If an oblong building is preferred, a house 12 ft. wide by 42 ft. long gives one hundred birds 5 sq. ft. of floor space per bird. Houses of such size should be from 4 ft. to 7 ft. high at the sides, and from 7 ft. to 10 ft. high at the highest point of the roof, according to the style of construction. [Illustration: Fig. 84. Good poultry house on a Kansas farm. (Photograph from Bureau of Animal Industry, United States Department of Agriculture)] =Feeding.= In the feeding of a farm flock the first thing to consider is what the birds can pick up by foraging. The poultry keeper on a farm, even more than the poultry keeper elsewhere, should make it a rule to do nothing for poultry that they can do for themselves. Fowls can do more for themselves at some seasons than at others, because natural food is more abundant. As fowls do not usually go very far from their house, the larger the flock the less food each bird will secure. On some farms quite a large flock of fowls can get all the food they need about the barns and stockyards and in orchards and fields near the homestead. [Illustration: Fig. 85. Poultry house at Mississippi Agricultural College.[10] (Photograph from the college)] [10] In this house the part of the rear wall above the roost platform is made to open wide, thus affording perfect ventilation in summer.