The Aves include all animals which have a body covering Of feathers and thus include pigeons. The Aves are divided into Families according to the vari ous chief characteristics, and the Pigeon belongs to the Dove family, which differs from all other birds in two respects: (1) They are the only birds that have a milk secreted in their crops at hatching time and which milk becomes the first food Of their Offspring; and (2) They are the. Only birds that hold their _'bills in the water when they drink. The duck, the goose, the swan and numerous shore birds will Often put their heads into the water, but that is not to drink, but rather to search for food, when such water — fowl drink they simply put their bills in the water and then raise them in the air to swallow.